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)