F6.3 & F7.4: Improper handling of custom mask/paste pads and thermal vias

[evanshultz]

We are using custom mask and paste pads as needed. Right now, this often generates a lot of noise because the footprint is constructed as desired but warnings and/or errors are generated.

Also, we have decided not to turn on mask for thermal vias and this violates the scripts' expectation for through holes. See KiCad/kicad-footprints#285.

These are two separate issues, but they often come together in the same footprints so I've joined them.

See KiCad/kicad-footprints#679 for one example. Here is the output from one footprint:

[poeschlr]

One simple way out would be to ignore this single rule if the footprint name has the suffix ThermalVias. Even better would be an additional check if the pad number matches a smd pad. Would this be acceptable as i think this would be easy to implement.

[poeschlr]

Ok there already is a pull request for adding a proper fix: #288