List all changes related to a build.

 - to do this, the column 'parent_changeid' was added to the table changes

Note:
 - I added a tab 'changes' for the build webpage. I think this should be modified in order to have something more readable (but my angularJS skills are very limited).
I'm having hard time understanding what this function is actually doing. 

If I understand correctly, I think it should be named getLatestChangeid()
and.. it should be documented.