code cleanup

Get rid of net_instaweb:: everywhere.  By eliminating the ngx_psol namespace we
can stop prefixing everything in ngx_pagespeed.cc with net_instaweb::

Fix other minor style issues.

Remove unnecessary declarations.

Rename ps_create_request_context to ps_route_request and CreateRequestContext to
RequestRouting because it no longer creates the request context.
Merge pull request #498 from pagespeed/jefftk-code-cleanup

code cleanup