Filter out hs/run for checkbashisms.

Ulimit -s is used there on purpose (#138).
Determine release name automatically

By default assume the chroot should mirror the version the judgehost is
installed on.
Allow users to self-register

Create a team/user for each registration. All teams created are assigned
the 'self-registered' category.
Chroot script enhancements

Add new script for installing oracle java
Add traps to umount things if the script fails