Configurable bitmap indexes: roaring and concise [do not merge yet]

Do not merge this pull request yet! More tests are required. All original unit tests pass at this point. I only want to start a discussion on high level changes. This also requires the 'fixup' branch in bytebuffer-collections

@lemire @ samytto - we require some more support for complementing in Roaring
@cheddar - if you only want to look at one thing, the changes to the queryable index interface are what bothers me the most
@xvrl @gianm @nishantmonu51 @drcrallen - would love to hear comments on the high level changes
 
Can this be part of the tuning spec? It seems that most other properties are handled through JSON. That way the information is also persisted in the logs.