[vassalengine] Default module folder: new feature?

[Pierre Miranda]

I don't know what's planned for the next release, but it wouldn't hurt
to be able to be able to configure VASSAL so that it always points to
a folder of one's choice (for example "my documents/VASSAL-modules")
when opening a module instead of VASSAL's root folder.
I'd rather have VASSAL point to such a folder than move all my VASSAL
modules to the VASSAL root folder for several reasons (mostly backups).