PoC backend on Flask-XMLRPC and Tornado

This implements a new backend engine for NIPAP that uses the Flask
XML-RPC framework instead of Twisted. Tornado is used to serve Flask
requests and allows pre-forking to handle multiple requests in parallel.

Authentication is performed similarly to how it was done with Twisted.
The request is mangled and a auth-object, produced by our AuthFactory,
is inserted.

The XML-RPC echo function now support sleeping for a specified amount of
time so that it becomes easier to test parallel requests.

xmlbench.py implements a small test benchmark that sends a bunch of
requests in parallel to the nipap XML-RPC API and measures the time
taken to respond. While not a complete and finished product in itself,
it comes in fairly handy for testing parallel requests.

Fixes #273.
Remove Twisted related stuff

Like the old xmlrpc.py which worked with Twisted as well as all
dependencies on Twisted.

Part of #273.
Add installation of Flask-XML-RPC

It's not available through the regular Debian channels, so we need to
build it from pip but use pypi-install for this to properly register it
as a Debian package.
Move flask_xmlrpc.py to xmlrpc.py

Part of #273
Add gzip compression

Use Flask-Compress to add gzip compression to the result we serve. This
should hopefully decrease query latency for large responses where client
and server are "far" away from each other.

Fixes #281.
Install Flask-XML-RPC and Flask-Compress using apt

Install python-flask-xml-rpc and python-flask-compress from NIPAP deb
repos instead of installing via pip/pypi-install.
Merge branch '273-flask-backend'

Conflicts:
	.travis.yml
	nipap/debian/control