WIP: Add incremental test scripts to misc folder

[Michael0x2a]

This commit adds some WIP progress scripts for testing or working with incremental mode in various ways to the misc directory. They all work, but I got a bit sidetracked today and didn't have time to fully polish them, but I figured I'd make a branch just for the record.

Greg also had the idea to generalize the test scripts I was using to test incremental in our internal Dropbox repos against any arbitrary repo, so I'll add a script to do that as well sometime over the next few days.

Todo:

• Add a more robust command line interface
• Probably get rid of misc/analyze_cache.py, since it's a bit too niche
• Refactor code between these scripts, and the other incremental script
• Add the generalized script Greg suggested
• Add some sort of "how to test incremental" doc

[gvanrossum]

Thanks Michael! If you want to polish these just send a new PR.