* 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.

Fixes issues with IDF file I/O on Windows (the famous 'ascii vs. binary' issue) and the reported problem of partial paths when KISYS3DMOD is specified.

* 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.

Modedit: now shows a specific layers manager, which allows user to select the technical layer which is used when adding a new graphic text or outline to the current footprint.
Please, note the layer manager was already available in GAL mode, but is was the same as tne board editor, which is not good.
Now:
- In default mode or GAL mode, the look is the same.
- Only suitable technical layers (i.e. paired layers) are selectable from the layers manager (for special purposes, some other layers can be used, via the graphic items properties dialog)

* Change Read to Load in Pcbnew and Eeschema preference menus.
* Make electrical rules check status bar message the same for both the menu
  and toolbar entries.

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.

Page layout selection: fix Bug #1405972, and add minor enhancement in page layout selection dialog (the new layout is shown after selection).
When the filename is not absolute, the page layout file is now searched first in project folder, and then in kicad template folder, if not found in project.

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)

Pcbnew: fix Bug #1404191 (Zone filling fails when a zone inside having the same net and a highter priority exists, which is allowed to manage different fill parameters )

Allows use of modifier shift key with letters A ... Z  in hot keys (including hot key editor). Thanks to John Bird, who helped me with his patch.

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

Looked like a minor issue, but was due to a more serious bug, when using 2 different DSN_LEXERS which were not synchronized.
The fix is not perfect, but unfortunately, the parser used to read the PCB_PLOT_PARAMS in .kicad_pcb files is also used in legacy board file reader.
Therefore it is better than write 2 parser functions, one for legacy files, the other for the .kicad_pcb files, which make the same thing.

BOM dialog: remove a not very useful button, and merge its function with an other (not perfect, need more work)
Add message box to show info added in BOM python scripts (See scripts/bom-in-python/README-bom.txt about this info)

Pcbnew, export Solder masks in Gerber Format: fix not working export when the solder mask minimal width is not 0 (the exported shapes were the same as if the vule = 0) with boost version >= 1.56
This is due to the fact the boost::pylygon function resize ( a inflate/deflate function) used for calculations does not work with boost version >= 1.56.
Use Clipper  inflate/deflate function instead. It is faster and works fine.

Modify usage of Inflate/deflate polygon in zone calculations, in order to be compatible with boost::polygon >= 1.56
Some code cleanup.