Marked most of the internal stuff as @private for EDoc.
Added gen_sock_stream as a set of internal modules.

Some renaming still required, though.
Renamed gen_* modules that don't define any behaviour.

Those came with the name only because my original project was named gen_*.
Updated documentation in gen_indira_sock_stream.
Updated some documentation a little further.
Providing default value for commander was a bad idea.

It should be left unset, so Indira can actually go down when it's not defined.
Updated documentation, mainly by filling examples_app_config.
Killed plenty of generic code in indira_tcp.

This is thanks to incorporating gen_sock_stream (as gen_indira_sock_stream).
Added an example command executor to documentation.