Added new function to download and unpack a repository from github.

Added
=====

* download_and_unpack_from_github grabs a zip file from a github
  archive, and unpacks it to some directory.
Changed to get component metadata from github repository.
Added wmt_get_db command to get component database from github.
Changed to not set sys.path in startup script.

Changed
=======

* Don't try to set the sys.path in the startup script. Instead, this
  should be done in the apache conf file. Use the python-path option
  to the WSGIScriptAlias command in httpd.conf.
Added __init__.py to make wmt.installer a package.
Added find_packages function to find all wmt packages.
Removed commented-out code.
Removed component metadata database from repository; it's now in its own repo.