Fix bug where (invalid) Connector names were created for mechanical holes.
Fix bug where (invalid) Connector names were created for mechanical holes.

The intention was that Connector names should only be generated for pins/pads
but it turned out we were also generating names (which were invalid,
e.g. "S1.null") for mechanical holes. This fix ensures names are
only generated for pins/pads connectors.

(This fix should really be made on the parent of this branch.)

Omniblox/Eagle-Loader,Omniblox/Eagle-Loader,Omniblox/Eagle-Loader