Added Prefix Option to run-crons.sh PID File.

Added configuration option 'PIDPREFIX' to add to PIDFILE name, so it will be unique in a multipool server.
Added ability to pass prefix as an argument when calling script.
Properly overwrite PIDPREFIX via command line argument
Added curly brackets to arg vars and removed extra empty arg catcher.
Added BASEPATH and SUBFOLDER configs for PIDFILE

Checks if the path exists, if it does not, it is created, if there is
an error a message is printed with the problematic path.
Fix PIDFILE folder check
Merge pull request #539 from nicoschtein/patch-1

Added Prefix Option to run-crons.sh PID File.