Remove unused/duplicated btagging code

This removes an unused track to jet associator, an unused tool that wraps the associator and some other b-tagging tools, and an unused algorithm that calls the the unused tool.

This code isn't used in trigger, reconstruction, or derivations, but it's named very similarly to existing code we do use, and it has a lot of overlapping functionality. It's built around an inheritance hierarchy that is similar to, but separate from, the one we use in our standard code. Basically the standard code we do use is evolution of everything I'm deleting here, but people seem to be maintaining both (probably out of confusion).

This makes figuring out what our code is doing very hard. Better to get rid of it.

@thuffman, @duperrin, this is a draft until I've verified that it doesn't change anything. [this is marked as ready.]