Add a jr() function modeled on jrun to execute things in jail on 9.1+
Do not use anymore jexec to get arch
Export MASTERMNT to simplify life
my_path() doesn't depends anymore on persistent jails
bset and bget can now take 1 or 2 arguments and use MASTERMNT and MY_JOBID to figure out path
Set MASTERMNT to the right variable
jail_runs now consider a jail is being run is the reference jail exists
Do not use jls anymore but rather things based on MASTERMNT