Optionally store statistics of processed requests in a sqlite file (or memory).
Added an option to 'manage.py server' which enables feat gateway running
on the same port at the specified prefix.

Currently the gateway isn't working there well (not acceptable response).
Add timeline graph presenting waiting times for a processing thread.
Visual improvements of the timeline graph.
Add a histogram type of graph for the waiting time.
Add statistics section about the request processing times.
Reogranize processing time statistics to store the view handler name instead
of the request path.
Add some usefull metrics on processing times.
Reopen sqlite file with statistics on SIGHUP if non-memory file is used.
Integrate the thread stats and query api to agent and standard feat gateway.
Prioritize image/png content type higher than application/json for internal
feat gateway if we are running with thread stats.
Fix wrong order or columns.