Use “adob--” as a prefix for private stuff.

Using dashes instead of slash (as in “adob/”) is more consistent
with ELisp code being part of Emacs.  At the same time,
“auto-dim-other-buffers--” is a bit long for internal functions,
thus it is abbreviated to “adob--”.
Consistently use “buffers” in function names, not “windows”.

The `adob--undim-all-windows' and `adob--dim-all-windows'
functions did not operate on windows but on buffers so the name
was a bit misleading.
Use a shorter lighter for the mode.
Bumped version to 1.5 and updated docstrings and comments.