Update init script for Ubuntu

I update the init script for Ubuntu to have more parameters.

Add parameter "CP_OPTS" : can use all CouchPotato's parameters from /etc/default/couchpotato
ie : CP_OPTS = " --config_file=/home/couchpotato/couchpotato.ini"

inspired by https://github.com/midgetspy/Sick-Beard/blob/master/init.ubuntu