Replace the hard-coded XPM icon in `InitGui.py` for the workbench
with an SVG file, which at this time is identical to the `Surface` icon.
Change `CMakeLists.txt` to properly install this new icon.
Rename all icons, so that all have the `Surface_` prefix.
Use the new icon names in the viewproviders and task panels.
Modifications for:
- let the surface workbench appear
- use only one Surface menu and toolbar instead of two separate ones
- create a Bezier surface using 2..4 Bezier curves (does not work yet)
- use enums for fill type
Signed-off-by: balazs-bamer <kolaloka@freemail.hu>
