improve expirer performance for sql backend

the model has been simplified which allows us to do bulk deletes
rather than looping through and deleting records individually.
this should improve performance significantly.

Change-Id: Ie99880438d7415d805a94d78df648082d5161417
Closes-Bug: #1289166
Move log alarms driver code to alarm tree

This change move the alarms related code of log driver to
the alarm storage subtree.

Partial implements blueprint dedicated-alarm-database

Change-Id: I366dafefedc5944a1b1ee8358933228ee5a4cb21
Merge "improve expirer performance for sql backend"
Merge "Move log alarms driver code to alarm tree"