Add generator for DIP switches sym & cmp

[ubruhin]

The first part for LibrePCB-Libraries/CK.lplib#10: generating symbols & components for DIP switches, to be added to the Base library. Generates DIP switches from 1 to 14 circuits.

Packages and devices for C&K DIP switches are under construction too, but will be added in a separate PR later (and belong to the manufacturer-specific library then).

Symbol of the 3x DIP switch:

Component of the 3x DIP switch:

So there is a symbol variant for a single, "combined" gate, and a "split" variant with each switch as a separate gate.

Everything was straight-forward, except two things:

First, I'm not sure about the look of the symbol. Often, DIP switches are drawn with circles, for example in KiCad:

This seems to be the IEEE 315 style, which we actually also support e.g. in the Relay components where we provide both European and American variants. Not sure if we really also should provide American DIP switches as this would then lead to 4 different symbol variants for each component 🤔

And second, I was not sure how to name the symbol pins and component signals. I have now named the pins like "5" and "5.2" (for circuit number 5) and the signals "5a" and "5b". This allows to display the pin name for "5", but hide "5.2" so the circuit numbers are visible in the symbol in a clean & lean way, though it feels a little bit hacky.

Any inputs welcome.

Library PR: LibrePCB-Libraries/LibrePCB_Base.lplib#164

[ubruhin]

Now also generating American symbol variants: