Bug 10094 - koha-list should have a --disabled option switch

Bug 10094 - koha-list should have a --disabled option switch

This patch adds that (--disabled) option switch, Also revisits some of the code and docs.

To test:
- Apply the patch and create new packages (you might just drop the koha-list command somewhere)
- Create several instances (koha-create)
- Randomly set some as disabled, others enabled and enable email on some.
- Test all possible option switches combinations

Expected results:
- koha-list should abort with a proper message if mutually exclusive options selected (--email vs. --noemail, --enabled vs. --disabled)
- koha-list should show the exact instances you asked for

Regards
To+

P.S.: I wanted to add the --disabled option switch for the tab-completion work I'm doing, but as of bug 4876 I thought it would be ok to revisit the script to make it robust and clear.

Sponsored-by: Universidad Nacional de Córdoba
Signed-off-by: Robin Sheat <robin@catalyst.net.nz>
Does what it says, and cleans up the script at the same time.
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>