Update docs with more detail

[SabineAuer]

• explain parameters for line types
• self admittance of nodes is not documented, yet
• explain functions, e.g inc() for perturbations
• update docs for wind turbine generator and renewable generator with inertial response

[lindnemi]

in the current docs most of the "source" links for node and line types, redirect to the julia base github folder, instead of the actual powerdynamics source code

[SabineAuer]

@lindnemi Mhh. I am not sure why this is the case. It is the same in NetworkDynamics since I wanted to check how it might look in a working example repo I looked at NeworkDynamics.

[lindnemi]

Oha. That's right! Thanks for checking!

I have no idea why, but will look into this on the ND side and report back.

[lindnemi]

JuliaDocs/Documenter.jl#1374

[lindnemi]

the source links work, documenter has fixed the issue