Version 4.0.3.3

This version adds (direct) support for Minecraft 1.13.2.

Additionally, it adds support for using an external program (by default, 7-Zip) to make backups (see #90), and fixes an occasional crash on entering singleplayer (#104). The external backup feature is somewhat experimental and I'm aware that configuration of it is a bit awkward and that it isn't reflected on the progress bar too well; I'll work on it more in later updates.