Implement keystone trust support

Also, correct lease db model. Now use trust_id, not trust

Change-Id: I676deb8a040e8b80194d1d9f9ab40e03b3bfa86d
Implement basic plugin for vm management

WORK IN PROGRESS

Change-Id: Ia34e16c636d1fa8d200873334f55b9868866f97f
Add event statuses handling.

Change-Id: I41ed9d8d5496ef261a045648620a89434627af24
Draft notification opportunity.

Implements email notification. That's only development/draft
implementation, because later notification mechanism will be
rewritten to be more configurable.

Change-Id: I24eeed6dc3c79d52c8195b59344ec2961e597bc6