List all changes related to a build.
 - to do this, the column 'parent_changeid' was added to the table changes
 - traverse the change graph backward from the current build until it found a change for which a successful build on the same builder had been performed.
 - use repository/branch/codebase of sourcestamps as a criteria to found the previous build
 - getParentChangeId to getParentChangeIds
 - parent_changeid to parent_changeids
 - update documentation
Fix sa2ajj's comments
indentation
Replace 'todo' in release notes
fix typo
Merge djmitche/buildbot:relnote-todone (PR #1389)
Merge pull request #1305 from delanne/Changes4Build

List all changes related to a build.