Reason: allow 'reason' to be overriden in Schedulers and show in Builder page
Reason: update docs and release notes
Omit changes that aren't in the DB from sourcestamps

Fixes #2554.
handle Deferred from fromChdict
handle BuilderConfig(.., mergeRequests=False); fixes #2555
Merge branch 'ShowReason' of git://github.com/jaredgrubb/buildbot
Trivial grammar fix
Merge branch 'master' of git://github.com/Ringdingcoder/buildbot