Initial EC2-API service commit.

This code introduces standalone service which proxies its calls to
existing nova EC2-API.
All the code here except for the ec2api/api/proxy.py,
ec2api/api/ec2client.py and some util functions is taken from current
nova and unused functionality is cut of it.
The proxy.py and ec2client.py files implement the new code which
proxies incoming request (on port 8788) to original EC2 API in nova
on port 8773.
The result is transparently translated back to user.

Change-Id: I4cb84f833d7d4f0e379672710ed39562811d43e0