Authentication integration tests: add proxy-router variants

[oberstet]

Since recently, we have fully automated integration tests for all authentication methods

https://github.com/crossbario/crossbar-examples/tree/master/authentication#test

This is using a router-worker only / single node setup.

We should add node configurations using

1. [x] one node with two proxy workers and a single router worker
2. [ ] three nodes with four proxy workers and two router workers per node

and automated authentication tests for all auth methods

[oberstet]

here are a first two:

• https://github.com/crossbario/crossbar-examples/blob/0f52db626fd1e1a9bfee1daaea1eeadc30bb08e9/authentication/wampcra/static/Makefile#L5
• https://github.com/crossbario/crossbar-examples/blob/0f52db626fd1e1a9bfee1daaea1eeadc30bb08e9/authentication/cookie/Makefile#L7