script: add script to start personal builder

This script HAS to be used by developer having an account on Suricata
buildbot. It MUST be run before doing a PR. It will trigger a build on
the branch and this will check the validity of the proposed branch.
The cinematic is simple:
 - Push branch XXX to github
 - Run 'prscript.py -u USER -p PASSWORD XXX'
 - Wait for the result
 - If successful, PR can be done
prscript: check if branch is synced with master

The script now check if the tested branch is in sync with current
inliniac's master.
prscript: exit when no build exists
prscript: add verbose option