When I Commit my Experiments, conflicts get dealt with intelligently

Summary: Essentially, we should think like git. This is a classic merge conflict, when two people have modified the same Property.

To make this work well, we will need to think a lot like git. We will need to be tracking the initial version of the Experiment, and compare it with the tree since then. We will probably need to have proper Text Change events in order to make this work right: not just recording the new version blindly, but actually recording the changes in the history, to make it easy to detect conflicts. This in turn probably implies that we need History working first.