Add support for recursive mod search, so players can organise their mods into subfolders:

Mods/
    Content Packs/
        [CP] Fixed Hat Mouse/
        [CP] Hobbit Hole/
        [CP] Rustic Travelling Cart/
    Cheats/
        CJB Cheats Menu/
        CJB Item Spawner/
    Loved Labels/

This is a common request, especially since content packs have taken off.

Done in develop for the upcoming SMAPI 2.8.