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
clean up event model

- fix defined relationships so they are properly backref
- fix trait_type __repr__ function to reference correct variable

Change-Id: Id606025ca3e91c6e9b7da597f8cc3181caf4d4b7
Closes-Bug: #1333399
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
Change of get_events and get_traits method in MongoDB and Hbase

This redesigns get_events method to generator style, with some additional
changes in unit tests and api.v2
get_traits method is also improved in this patch, additional sorting was
removed from get_traits method.

Closes-bug: #1339626
Change-Id: Ie65cc6f6c85eab53847176273b27de693bd2052f
Merge "improve expirer performance for sql backend"
Merge "Move log alarms driver code to alarm tree"
Merge "clean up event model"