Xfce development and release model

[Nick Schermer]

Few notes/questions:

- In the branch image there is 'No change', looks a bit weird. You can
still commit bugfixes and translations in master while working in a
feature branch right?

- There is, 'The release team always picks the latest available
development release of each component for pre-releases and the final
release', should be latest stable release I guess?

- I'm not really a fan of the ELS branch, personally I would prefer a
small period after the final tag where only bugfixes and translation
updates are allowed, like we did with Xfce 4.6.0 -> 4.6.1, then create
a stable branch from the 4.6.1 master.

- Maybe mention the buildbot somewhere, which monitors the master
branch all the time. Maybe even an (unofficial) rule that no feature
branches are merged in master while the buildbot reports a broken
master (fix before you continue!).

Nick