Increase customizeability of monasca

monasca has several places which, after some tweaking, could be made customizeable.
Such modifications would allow new monasca services to tweak existing configuration.

Identified locations
- alarm states
At the moment monasca is based on fixed list of alarm state. However database model supports adding new states. The idea is to allow another monasca service (a.k.a. monasca-events or monasca-maintenance) to add the states such service would understand and control. Also it should be possible to query those states, components like monasca-ui should understand that there's actually more than just 3 possible states)
- adding ability to globally suppress alarm transition
Currently there is a similar solution for notifications (actions_enabled flag). The idea would be to allow another monasca service to "tell" the threshold engine not to evaluate the certain alarms.
- dynamic alarm actions
Along with the custom states it should be possible to send notifications upon alarm transition into such state.