Improved the function 'is_graphic_symbol' to include testing if a footprint is specified.
Improved the function 'is_graphic_symbol' in file kicad_sym.py to include testing if a footprint is specified.
With reference to S7.2, a Graphic symbol does not correspond to a footprint. So if a footprint is specified, the symbol does not qualify as a graphical symbol. Therefor rules in S7.2 does not apply to the symbol under test.
The current function tests if the symbol has no pins (which is correct), but does not check for a footprint value.
An example of such is a spacer underneath a 3 mm LED or a TO-92 transistor. It would have no pins, but will have a footprint with a 3D step/wrl.