fix FreeBSD init script

-add actual start command
-fix verify_couchpotato_pid function, 'ps' command failed if PID var was empty
-fix verify_couchpotato_pid usage, acutally use the return of verify_couchpotato_pid in the 'stop' routine
Don't influence the PATH variable in FreeBSD rc script

Don't prepend the PATH variable, it's ugly, unwanted and unnecessary. Call binaries with their full path.
Acutally use config_file variable
Redo FreeBSD init script completely.

Use rc.subr functions and proper rc.conf variables.
Remove services that are not required for couchpotato to run