[Bf-python] Support listing of multiple versions of the same addon

[Jason van Gumster]

Nathan Vegdahl <cessen at cessen.com> wrote:

> A topic that has come up over on bf-committers is the possibility of
> supporting multiple co-installed versions of the same addon, without it
> showing up as a conflict in the addon browser.

A complication I see with this is in the event that the user actually enables
both (or more) versions of the add-on. Assuming that the add-on(s) make
additions/overrides to the UI in the form of panels, menus, and hotkeys,
there's no easy way to differentiate what UI element belongs to which version
of the add-on.

So perhaps I'm stating the obvious, but in order for this to work, a check
should be included to prevent multiple enabled instances of the add-on. The
question then becomes: how does that get implemented and enforced?

  -Jason