Document HBase configuration

The instructions to configure HBase as the database backend for Ceilometer

Change-Id: I3c79e68db7226531d77037bc93ca2cca3ef7db28
Fixes: bug #1174326
Don't use trivial alarm_id's like "1" in the test cases.

Change-Id: I5702409b60ec6f0dd8fcc4338c9fe100c289bb36
Add the sqlalchemy implementation of the alarms collection.

blueprint alarm-api
Change-Id: Id8f00b1cb7519ca59f277170fcb03e0976a4fb1a
Merge "Document HBase configuration"
Merge "Don't use trivial alarm_id's like "1" in the test cases."
Merge "Add the sqlalchemy implementation of the alarms collection."