Deprecate TCMS_RAWURI in favor of TCMS_BASE

[todd]

Currently (0.6x), we use the Apache PythonOption directive to set TCMS_RAWURI when we're configured in a <Directory> block, to indicate which to use: the request URI vs the Path Info. This is a pure kludge. I'd like to use TCMS_BASE set to /<Location ($1)>/ instead, and then have the apache handler (in ApacheEntryPoint.py) wrap the apache req in a request object that deals with all this stuff.