Bug 33105: Add vendor issues

Bug 33105: Add vendor issues

This patch is the main patch of this patch set, it contains the
controller acqui/vendor_issues.pl, its corresponding template, and some
links to this script.

It adds:
* A new DB table aqbookseller_issues linked with the aqbooksellers table
* A new subpermission acquisition.issue_manage
* A new authorised value category VENDOR_ISSUE_TYPE and two examples
MAINTENANCE and OUTAGE
* A new controller couple acqui/vendor_issues.[pl,tt]

Test plan:
0. Apply the patches, run updatedatabase and restart_all
1. Go to the acquisition module, create a new vendor or use an existing
one
2. Create a couple of issues for this vendor
3. Edit/Delete and search for those issues

This is the basics for tracking issues with vendors.
Suggestions welcome, on follow-up bug reports.

Signed-off-by: Jonathan Field <jonathan.fieeld@ptfs-europe.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>