refactor geda.py:Generator.add_pad
port geda generator to use str.format instead of % formatting
Fix overlong lines and regularize spacing in geda.py

* Where possible lines over 80 characters where broken (exception:
  the long string templates)
* Spacing of operators was adapted to follow PEP 8
Add silk_circle and silk_arc methods to geda.py

*Please note: I had to guess as to the semantics of the "silk_arc"
 method, it is well possible it will not always produce the desired
 result, regression testing against the kicad generator should be
 done (by someone with access to kicad)
Leave the pcb footprint header fields blank

*These fields are filled by pcb or gsch2pcb, and should be
 left blank in footprint files
Fix line-width for pads in the geda.py generator
Fix the radius of circles, the pcb format is strange ...
fix previous commit
Fix qfn footprint generation

* The qfn footprint generator used homebrewn pad-row creation
  making severe mistakes (horizontal and vertical pads
  in the packages did not have the same dimensions)
* If this breaks the kicad backend, the kicad backend must be fixed
Correct checks for options for silkbox and placement of markers
Merge branch 'fix-geda' of https://github.com/sebastianriese/footgen

Conflicts:
	footgen/geda.py