Some site Administrators want to be able to delete or publish draft
changes or patch sets even though they are not the owner.
Allowing members of the Administrators group to do this by default
would not follow the principle that being in the group "does not imply
other access rights", so instead add two new permission categories
"Delete Draft Changes" and "Publish Draft Changes" which can be
granted to the Administrator group, or indeed any other user group.
Bug: Issue 1675
Change-Id: I37083544242a81d3d7fff0950b2edcd9fbe92ebf
be7f458826