Add commit msg requirements infra #agreed to

Add needed-by: and depends-on: refs to commit messages as agreed to in Summary #4 [1]
Add gerrit topic to use: "module-split"

[1] http://eavesdrop.openstack.org/meetings/infra/2014/infra.2014-10-28-19.01.html

Change-Id: I049cbf890d811c5eac2633a857ab9744314bdc93