debugging-layout: create new directory, move and add information

This commit is a result of squashing debug-layout branch by Janek,
and it was REBASED onto 091d3ade087 for the sake of cleaner history.
Thus, it adds some content that was removed earlier. I'll delete
it again.

Also, i stripped trailing whitespace from debug-layout branch when
squashing it.
add debugging-layout category in README