update reward distributor to support owner override

[dbeal-eth]

adds a new method to rewards manager module, distributeRewardsByOwner, which allows for an owner of the pool to change the rewards distribution setting outside of RD operation.

notes:

• it was previously intended that RD should always drive the distribution settings on the core system. however, there doesn't seem to be any downsides in allowing pool owner to have control over the distribution as well, and can provide a helpful lever in recovering from errorneous situations such as these
• renamed the function instead of overdubbing the same method to prevent confusion in function, since there are a lot of params for both and they look similar.
• tests added