Add a generator for capacitor networks.

[Doeme]

This is basically just a copy of the R_Networks code, with some minor (i.e. drawing capacitors instead of resistors) and sedding s/resistor/capacitor/g.

It spans the following types:

• C_Pack: Multiple capacitors in one package
• C_Network: Multiple capacitors with one lead in common

It is still lacking the proper footprints though.

Here's an example of one network (or rather pack)

[poeschlr]

Is there a symbol pull request?

[Doeme]

Alas, there is not, since I have not figured out how to auto-generate the footprints yet (and for the project that spawned this pull request I hand-crafted the one needed).

I've found some kicad-integrated generators (reached by the footprint-editor), should these be used?

[poeschlr]

https://github.com/pointhi/kicad-footprint-generator

[Doeme]

Oh, ok, cool. I can at some point include the C_ARRAY footprints there, but at the moment I'm rather preoccupied. It'll probably be 2 months until I work on it again.
If somebody wants to step in: feel free! ;)