New config system and other goodies.

• Moved much code from jailadmin to Jail.pm, making the command-line client much "thinner" than before. In the future, alternate frontends may be preferable to the current utility and this should make it much easier to develop them.
• jail-snmp: Redirected STDERR to /dev/null to prevent some spurious errors whenever debugging is enabled.
• jail-snmp-persist: Added a new persistent version of jail-snmp that runs with much less overhead than the older jail-snmp. Update your SNMP daemon's configuration to use this instead of jail-snmp if at all possible.
• jailadmin.conf.sample: Added many comments and a few new options:
• fstab: Define an alternate fstab file to use for (u)mounting jailed filesystems.
• shutdown: Set to "naive" (default) to retain current shutdown behavior, or "emulated" to execute /etc/rc.shutdown within a jail.
• startcommand: Specify an alternate jail startup command.
• usejtools: Use the new jls and jexec commands for faster and more accurate jail operations (and also removes the necessity of mounting /proc in the host environment).
• Easier definition of named groups, due to:
• All new config parser that allows multiple blocks of default settings. Side note: Did I mention that I hate writing config parsers? Well, I do. If someone wants to donate a new parser, I'll be more than happy to accept it.
• Jail.pm: Many changes and enhancements:
• As mentioned above, Jail.pm can now use jls and jexec to interact with the jails and gather information about them. This is disabled by default for compatibility's sake, but should be enabled if you have access to these commands and don't experience problems with them.