Bitmaps are now identified by an enum class instead of by pointers.
Bitmap loading and caching is now handled by a class in common, and
we no longer compile most bitmaps into the binary, so there is no
longer a bitmaps static library.
Instead, bitmaps are archived to a .tar.gz file which is installed
in ${KICAD_DATA}/resources/images.tar.gz
The source PNGs are checked in to Git as the original CPP files were,
so that people can build without the required dependencies to convert
SVGs to PNGs.
Initial support is also added for dark theme icons, although this
is not yet exposed in the GUI.
Stubs are present for multi-resolution image resources, but this is
not fully-baked yet and could use some refinement.
This leaves them untranslated internally but makes sure their
translation strings exist so they can be dynamically translated
at the GUI level.
Fixes https://gitlab.com/kicad/code/kicad/issues/6020
Jon Evans
Jeff Young
Dominik Wernberger
Wayne Stambaugh
jean-pierre charras
Marek Roszko