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).
Page layout editor: Add bitmap items to the page layout existing items.
Now a bitmap image can be added to a page layout description. Currently the bitmap is expected having a 300 ppi definition.
Note: not all plotters can plot a bitmap, and in this case the bounding box is plotted instead of the bitmap
Remove KICAD_GOST option because it is now useless: the 2 GOST options are now selectable at run time and are:
* specific page layouts (now user definable, and the GOST page layouts are available in template folder)
* notation for multiple parts per package (made in eeschema, preference menu)