Rename send/recv to import/export

This opens up some space to post/get via send/recv.
Make a Topics module more formally
Sketch out projections
Add projections to Topic
Fix a bunch of issues in the projection code

Histograms were being calculated incorrectly, code in general was a bit
inefficient.  Now chained tranforms will also be supported.
Add xyz_to_xy_by_z_max projection
Fix generation of tables.cql

Starting work on the IIITopic revealed some issues in the algorithm.
Make Topic work better for non-IITopic types
Add IIITopic
Fix indentation in the README