Repair group fixes

[KJeff01]

This PR fixes the repair group feature in a few ways:

1. Interrupting a droid going back to repair (or base) would leave the group number red forever until it was brought back to full HP. This is due to droidWasFullyRepairedBase() not being called when breaking the droid out of the retreat-like order, and that might not be a good idea as it restores the group from the repairGroup, as well as updates the groups UI.

2. Saves and loads a droid's repairGroup, and the productToGroup for factories.