Fixup handling of git repo and document process

After reading up on how the Ubuntu process was supposed to work, I found that a few things were being broken by our adjustments to it.

1. The detection of the previous release commit in the git log was broken by using "release x.y.z" instead of "Ubuntu-x.y.z". Fixed the rules command to detect either.
2. startnewrelease breaks with our endlessN local revision. I added a separate rule, startnewendless, that just bumps the local endless version and starts a new changelog entry for it.

I added a README.endless documenting the process including those changes. I also went back and made a commit for my previous endless2 version to get the tooling to respect it correctly.

[endlessm/eos-shell#2840]