We eventually want to be able to compress chunks in the background as
they become old enough. As an incremental step in this directions, this
commit adds the ability to compress any table, albeit with an
unintuitive and brittle interface. This will eventually married to our
catalogs and background workers to provide a seamless experience.
This commit also fixes a bug in gorilla in which the compressor could
not handle the case where the leading/trailing zeroes were always 0.