Send-signal, payload if hook does not exit and cleanup.

* So, if "send-signal" is set in the hook.path field, a signal will be send with the repo, info, user and request. This allows to process the hook in an attached python method instead of a command /shell script that has to have the correct mode etc.

* The payload will be passed if hook does not exist.
@sesas my main objective was to bypass the ``hook.execute()`` and use a signal instead. 
The second point was not "to repeat myself" and copy paste the code from L28 .. L32 to access the payload in case that "nothing matches" and use the payload for further processing. There is no need to merge this PL - as always - it's a suggestion. Not sure what this is all about? This discussion brings no added value - at least not from my perspective.