JSAN module autoloader for "add-ons"

JSAN module autoloader for "add-ons"

This adds a "Server Add-ons" menu entry under Admin -> Workstation
Administration in the staff client.  Choosing this allows you to edit or set a
list of identifiers that correspond to JSAN-style modules found in
/server/addons/, and is meant mainly for activating 3rd party modules within the
staff client on a per-workstation basis.  You need the
ADMIN_SERVER_ADDON_FOR_WORKSTATION permission to use it.

Configuration options for activated add-ons may also show up in this interface.

More technical details:

This Server Add-ons list is stored as a JSON array in the Mozilla preference
'oils.addon.autoload.list'.

We also add an addon.autoloader module that gets called in most XUL interfaces
via the util_overlay file.  This autoloader will loop through the modules
specified in 'oils.addon.autoload.list' and instantiate each, storing a
reference to each of the newly created objects in a data structure in
window.oils_autoloaded.

So, as an example, let's say there is a module: /xul/server/addon/uber_scan.js
And we have the identifier 'uber_scan' in our Server Add-ons list.  Then, on
every page load of a XUL interface using the stock util overlay, we will
effectively call:

    new addon.uber_scan();

Causing the code in the module to execute.  It is up to the module to determine
whether it needs to do anything within a given interface.

Signed-off-by: Jason Etheridge <jason@esilibrary.com>
Conflicts [permission numbering]:
	Open-ILS/src/sql/Pg/950.data.seed-values.sql