Bug 18562: Tab completion in bash

Bug 18562: Tab completion in bash

This patch adds the fancy tab completion in bash.

To test:
- Run:
  $ source debian/koha-common.bash-completion
  $ sudo koha-sip <tab>
- Play with all the options
=> SUCCESS: The combinations make sense (e.g. only SIP-enabled instances
  are completed for --start, --stop, --restart, -v and --verbose are not
  offered if the other one is already in there, --enable only applies to
  SIP-disabled instances, etc).
- Sign off :-D

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>