create and extract conda packages of various formats

 Cph is an abstraction of conda package handling and a tool for
 extracting, creating, and converting between formats.
 .
 At the time of writing, the standard conda package format is a .tar.bz2
 file. That will need to be maintained for quite a long time, thanks to
 the long tail of people using old conda versions. There is a new conda
 format, described at https://docs.google.com/document/d/1HGKsbg_j69rKXP-
 ihhpCb1kNQSE8Iy3yOsUU2x68x8uw/edit?usp=sharing. This new format is
 designed to have much faster metadata access and utilize more modern
 compression algorithms, while also facilitating package signing without
 adding sidecar files.