Unify and simplify inline documentation of all possible entry points

* Replaces multiple URLs with a single URL per file.
* Reduce long "do not use this because you should not use this, see
  the documentation on how to properly use this" comment with a
  single line. ;-)
* Add welcome message by Lydia.

Change-Id: I3eeb704dd8ab923fed7a17280ad4fceaab9b2e0c
Merge "Unify and simplify inline documentation of all possible entry points"