Differences from v4 and v5
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pad options (module/pad/options):
	options/anchor: circle or rect; used for conneciton calculation -> ignore
	options/clearance: outline or convexhull: clearance shape -> warn for convexhull

new pad shapes (module/pad):
	roundrect
	roundrect_rratio
	custom

probably for pad shape custom:
	module/pad/primitives -> multiple gr_arc, gr_line, gr_circle, gr_poly

model offset: 
	module/model/offset: 3d model offset in x;y;z direction -> ignore

multilayer zone:
	zone/layers -> (maybe used instead or layer?) multi-layer zones, used for keepout -> split them up on import

new net_class properties:
	net_class/diff_pair_gap -> ignore
	net_class/diff_pair_width -> ignore

Ignored/removed:
	general/no_connects - not supported any more?