Create icons for the nodes

[luzpaz]

UI/UX request: https://forum.freecadweb.org/viewtopic.php?f=34&t=41432

[microelly2]

I started to create some icons

naming convention:
if nodename is FreeCAD_Box
the icon is freecad_box.svg, size 64 x 64 in
.../Mod.PyFlow/NodeEditor/PyFlowPackages/PyFlowFreeCAD/UI/