Updated test client to use a *supported* means of adding extra CA certs.
Cleaned up client test code, updated `ca_trust.py` with supported API for adding CA certs.

Updated the reverse proxy code to use the supported `ca_trust` module.
Refactored some functions related to URL manipulations for proxies.
Started to replace hard-coded proxied app support with plugins.
Completed the Grouper plugin for the authenticating reverse proxy.

Added a plugin interface for intercepting the service URL passed to CAS.
BUGFIX: The grouper plugin was comparing a complete URL against a URL path.