WIP: Import options - better gopilosa.StatusChan support

[travisturner]

I'm just putting this PR here so you can see what I changed in the PDK in order to get the StatusChan to work. It builds on top of #78. There are still some issues. It assumes that a frame contains only one of:

• a standard bit frame
• a single BSI field
  Even with this limitation, and protection in the PDK, there is a still a potential panic situation (closing of a closed channel) in go-pilosa that I marked with a TODO in a PR to that repo.

The general idea here is that StatusChan is frame-specific, so I made it part of the FrameSpec instead of provided as a functional option for the entire index in SetupPilosa().

I don't think it's necessary to merge this PR into master, but we'll need to consider all of this as we refactor Pilosa. I think the Frame to Field logic will help because that will effectively enforce the limitations listed above.

[travisturner]

fixes #79

[jaffee]

a decision on FeatureBaseDB/go-pilosa#141 will have a significant bearing on this.

passing the statusChan in the importOptions per frame seems fine to me. Note that the PDK will also auto-create frames if they aren't set up initially. We might consider adding a method to the Indexer to get status chans for these frames at some point.