Add additional path for collections

[haubourg]

Hi there, I 'm configuring a QGIS package for my organization. Just as it is possible to add additional paths for plugins or SVG, it would be awesome to be able to add additional paths to collections.
The idea is to have centralized read-only drives where we pre-package all those resources.
A user adding manually new collection shoud however still have them written in its own user profile.

I'd be glad to help here if this seems a good ide, this is quite high in my todo list.