Package.compress_package: correctly use relative path

Fixes #7102.
Package.compress_package: fix for files, period in name

* If a period is in the name of a directory package that is being
  compressed, os.path.splitext() splits the name of the directory
  as though it were a file extension.
* If full_path was a file and not a directory, the rsplit and subsequent
  join produces incorrect results, e.g. for /path/to/aip/name.7z:
  /path/to/aip/.7z instead of /path/to/aip/

Refs #7102.
postrm: fix to ensure upgrades work

added logic to debian/postrm script
to prevent files from being deleted during upgrades
Add preinst script to work around 0.3.0 postrm
Use storage_service.log universally
Restructured/cleaned up doc dirs, added plugin.

Cleaned up the documentation directory and added Sphinx REST API
documentation plugin. Added documentation skeleton for REST docs.