This adds an icon to the left of the row with an error symbol if the
file can't be found or opened, and shows a tooltip over the icon with
and error string.
Fixes https://gitlab.com/kicad/code/kicad/issues/3815
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.
ADDED Eeschema-specific netclass settings including wire and bus
thickness, color, and line style.
Netclasses override individual wire & bus colors and line styles.
If that proves an issue we might look at something more sophisticated
with inheritance.
Fixes https://gitlab.com/kicad/code/kicad/issues/4581