Cellxgene

This is largely a performance and refactoring release, with a few small bug fixes.

Changes:
* Performance improvements throughout application, due to introduction of a new internal data model and other refactoring (588, 590, 611)
* 610 fixed - Reset slow for large datasets
* 617 fixed - negative scalar annotation and expression values were incorrectly displayed

Fixed
* Failed pypi upload due to previously deleted version

Added
* Lasso selection tool
* Add list of genes

Fixed
* (ivirshup) Serving cellxgene through reverse proxy
* Does not error if Content-Type header also include charset
* De-duped -d CLI option alias for launch: kept the alias for --diffexp, removed from --debug

Fixed
* ModuleNotFoundError: No module named 'server.app.util.fbs'

Added
* Performance improvements facilitated by switching to binary (using flatbuffers) for data transport
* Scatterplot any two genes
* Async busy indicators on slow operations
* Non-finite values displayed as gray on graph when coloring by a field and elided from histograms
Fixed
* Can now run cellxgene container on remote host
* Disable cell set buttons until differential expression is cleared
Removed
* CLI param --nan-to-num removed (non-finite values can be serialized after switching to binary transport)

Changes
* Add cluster occupancy - when coloring by categorical metadata, stacked barchart shows proportional breakdown of other categorical fields. E.g. color by gender, evaluate gender makeup of each cluster
* Add Docker support