add dependency and apply dependency objects

Signed-off-by: Nick Chappell <nick@intronic.org>

Icinga refs#7219: https://dev.icinga.org/issues/7219
Changelog updates.
Little Changelog fixes.
Fix little typos.
Whitespace cleanup.
Always include Class apt on Debian, needed by apt::source

In addition some indention fixes.
Use actual debmon.org repository key

29D662D2 is the actual debmon.org key
BC7D020A is Alexander Wirt's (formorer) old key