Allow batch mod install

[ronlaws86]

At present MO2 only allows for a single mod to be installed at a time; this is fine if you are building your list 1 by 1 or over time, but if you have a copy of all your favorite mods downloaded and stored somewhere as their original archive files and there are say, 100+ of them, then doing this by hand 1 at a time manually is honestly a form of torture.

MO2 could really do with an option to either select multiple in the open file dialog, or a supplementary install multiple option in the file menu so that one can batch install a large collection of mods in one go.

I know it's possible to place the archives in the downloads folder, but again the downloads section on the right does not allow the selection of multiple items, so this does not really negate the aforementioned torture, it only swaps the open dialog step with a scroll and select step.