Minor fixes: make a message translatable in CvPcb. Dialog choose component: fix a missing min size calculation and make min size bigger.

* Create new dialog to edit environment variables.
* Add helper class ENV_VAR_ITEM to manage environment variable values and
  if they were defined externally.
* A path configuration dialog access to KiCad, CvPcb, Pcbnew, and Footprint Editor
  window menus.
* Add validator for environment variables.

* Make OK button the default action in the 3D viewer option dialog per UI
  policy.
* Fix standard button sizer padding in 3D viewer options dialog.
* Let sizers do their job by using default size for 3D viewer options
  dialog.
* Set 3D viewer hot key to Alt+3 in all parent windows where 3D viewer is
  accessible.
* Minor code cleaning and coding policy fixes.

* Add footprint and drop table from the Pcbnew footprint library table menu
  entry to make it clear to new users.
* Add component to the Eeschema library configuration menu entry.

Cvpcb: Shows a better message when a netlist is not found.

Fix minor bug #1429990 (3D viewer shows hidden footprint graphic texts ). Fix minor coverity warnings (not initialized members and dead code)

Minot fixes: Minor coding style issues fix (tab -> spaces). Add missing GetClass to all classes derived from EDA_ITEM. Make debug method Show() only compiled in debug mode.

* Fix default KISYSMOD/KISYS3DMOD (#ifdef typo) for OSX builds.
* Remove setting KIGITHUB from kicad/pcbnew Info.plist in favor of hardcoded default
  setting for OSX builds.
* Remove now unneeded Set3DShapesDefaultPath() and other small things.

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.

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.

Cvpcb: fix a typo which prevents cvpcb to be compiled with webkit suppport. Equ files support enhancements.

* Add dialog to edit the list of active equ files.
* allows use of our environment variables in .equ file names.

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).

Cvpcb: Add a tool to solve conflict assignments when the schematic netlist and the .cmp file do not contain the same assignment and both are valid fpid.
It happens when footprint assignments are modified outside Cvpcb (when editing the footprint assignment field in schematic)

Kicad manager: fix Bug #1385953 (unable to open .PDF files with spaces in name/path when using default PDF browser).
Fix also an issue when selecting preferred browser.

* Fix creation of single app bundle with respect to scripting support.
* Cleanup scripting search paths for OSX.
* Fix some small CMake bugs from previous OSX build change.
* Optimize bundle file structure to be consistent with Apple specs.
* Add helper script for compiling wxWidgets and wxPython
* Update OSX build instructions.

* Compile all binaries into a single application bundle.
* Use CMake BundleUtilities to make application bundle relocatable.
* Restructure build output to directly create an image file.
* Fix default search paths.
* Set KIGITHUB environment variable.
* Added patch to fix wxWidgets so names for OSX.