Add vision specific featurecoordinators

FeatureCoordinators for disparity, ocularity, spatial frequency and motion are added. This pull request depends on the related ImaGen pull request (https://github.com/ioam/imagen/pull/30). The motion feature coordinator needs time_dependent to be set to true.
I think this will break some of the tests that depend on lissom.ty, at least those having to do with snapshots.  That's not a long-term problem, as those tests should all be updated to use your new framework, but I'm not sure what to do in the meantime.  Is it simple to replace this with the new Sweeper in this one file?