Pcbnew: fix Bug #1418135 (scrollbars never shown in design rules dialog, in netclasses grid list, which prevent to use many netclasses). Also fix very minor other issues.

Pcbnew - plot dialog: fix Bug #1417435 (Gerber(and some others)  plot mode is fixed as”sketch” instead of "filled" )

Dialogs edit footprint in module editor and edit footprint in board editor: add button to edit the selected 3D shape filename.
Dialog edit component in library editor: add button to edit the selected footprint filter.

Pcbnew: simplify draw code in  default canvas and plot functions by removing the plot LINE option, which is not existing in all plotters, not existing in opengl/cairo canvas, and not usefull in default canvas.

ModEdit: add a settings menu option(and the corresponding dialog) to set default values used when creating a footprint or add graphic items to a footprint being edited.
These settings are now not common to the board editor, because the footprint editor can be run outside the board editor.
download_boost.cmake: ignore  .htm* files when installing boost. They are not used, and often have a very very long (and stupid) name which sometimes creates issues.

Fix minor aesthetic issues in dialogs (these minor issues (overlapping widgets)  exit only with some Windows managers like KDE)

Minor and very minors fixes: move -DKICAD_USE_WEBKIT definition to the main CMakeLists.txt. Remove duplicate semi-colon at end of some lines.

* if the current select plugin is the github plugin, one can select some of these libraries and add them to the table
* if the current select plugin is the kicad plugin, one can select some of these libraries and download them to make alocal copy.
  They can added to the table after they are downloaded.

* Make generate button the default in Eeschema netlist dialog.
* Fix spacing issues in export IDF dialog.
* Make OK button the default in export IDF dialog.
* Remove unnecessary end dialog code from export IDF dialog.
* Improve resizing of export IDF dialog.

Add hight contrast option in Modedit. In hight contrast mode, solder masks and solder paste are shown.
this option was possible only by modifying the way display options are managed.
before these changes, display options were a global DISPLAY_OPTIONS class instance.
Now each EDA_DRAW_FRAME(and derivated classes)  includes its own DISPLAY_OPTIONS class instance.
As a consequence, some duplicate display option variables in these classes have been removed, because there were just duplicate variables of the  DISPLAY_OPTIONS class instance.

Cvpcb: force project name in stand alone mode, to allow access to project fp lib table. In project mode: disable the read netlist option (the netlist is read when Cvpcb is started by eeschema)
Dialog fp lib table editor: now shows the table full filenames, to help users.

Remove a duplicate code for dialog select dir list.

Fix issue when using a page layout file in project folder: eeschema and Pcbnew did not use it, unless using an absolute path.
Now, if the file path is nor absolute, it is seen as relative to the project (which is the expected behavior)
fp lib wizard: when pcbnew id compiled with USE_GITHUB_PLUGIN=OFF, the github plugin option is no more accessible (and the web viewer no more used).

Freeroute dialog: remove freeroute access via java web start, because freeroutecanot be run now via java web start.
freeroute.jarcan be run by Kicad, as long freeroute.jar is found by Kicad (for instance if it is in kicad bin folder)

Minor fixes. Remove unused icon. Add 3 new icons. Change one icon (3 icons are from Konstantin Baranowskiy)

Fix remark 1 in Bug #1393277 (the option "use absolute paths" acts reversed: ticked exports relative paths, unticked exports absolute paths)

- re-worked PNS_LINE_PLACER and PNS_ROUTER classes a bit, removing duplicate class members
- cleaned up Andrew's blind/buried via fixes
- fixed 'custom via width' dialog bug updating the width even when closed/cancelled
- fixed incorrect radius of drawn microvias

* Fix assertions in Eeschema when editing net labels, electronic rules check,
  and plotting.
* Fix assertion when opening PCB calculator.
* Fix assertions in Pcbnew when changing footprints in footprint properties
  dialog and adding or editing text.

Eeschema, Plot dialog: add Plot directory selection. The patch from 1383026@bugs.launchpad.net was widely used.

* Improve VRML export dialog lay out.
* Make the OK button the default action in the export dialog.
* Make 3D model export work correctly and avoid redundant file copies.
* Fix embedded path separators in wrl files on windows.
* Fix absolute model file path creation in wrl files.
* Clean up VRML export code.

* Remove obsolete settings from Doxygen configuration file.
* Fix some Doxygen warnings.
* Add the board edge segment snapping to developers road map.
* Fix some coding style issues in CMakeLists.txt

Pcbnew: fix Bug #1373468 (Non Copper Zones Properties  dialog "Layer selection" empty) (Linux specific)

Minor fixes: specctra export: skip malformed circles (having a radius = 0)  in board outline creation, which can crash 3d-viewer or vrml export.
dialog_fp_lib_table: remember during a session the last open table (global or local).
drawing_tool: fix compil warning
Update demos.

* Set wxGrid tab behavior to leave grid when using the tab key.
* Lots of coding policy fixes.