Readd missing thumbnail

Change compatible version to 1.3.*

Revert the last update adding a compatibility change to More Game Rules: changing the description of the MGR Cadet Branch game rule to reference that this mod supersedes that game rule.

The change itself worked fine, but would result in a ghost game rule when MGR was not installed, and I don't think there is a way to conditionally create game rules?

Added compatibility with the More Game Rules mod.

Updated description and thumbnail.