Support composite rules alarm and deprecate combination alarm

Currently, the combination alarm evaluation process have some potential problems. in blueprint [1], ZhiQiang Fan has described 3 main problems, And he has done some efforts to solve this these problem,
but the change is complex, and there are some reason that proposal is hard to address the problems. The main point need to be considered is how the change works PartitionCoordinator.

It would better to propose a new type alarm that can be attached multiple evaluation rules. the composite-rules-alarm allow users create alarms with specifying multiple rules combined by logical operators, for i.e. we can create an alarm that will alarm when: *mem_util>=0.9* OR *cpu_util>=0.9*.
The conveniences of this proposal are:
 - The triggering condition of alarm based on multiple statistics is visualized. Unlike the combination alarm which we need to get the dependent alarms to know the triggering condition.
 - Can avoid the 3 problems described by ZhiQiang Fan in the blueprint[1]
 - this proposal will make alarms easier to manage because it will reduce the amount of alarms.

[1] https://blueprints.launchpad.net/ceilometer/+spec/resolve-combination-alarm-dependency-chain