Add Protractor test framework for e2e tests

@gashcrumb - added in Protractor tests so we can do integration tests deployed inside containers. atm this just means using jetty plugin to deploy war & running tests against that. Obviously only tested on Linux, but any chance you could try it out on Mac & W-W-W-Windows if you get a mo?

Want to expand that to support Karaf/Tomcat deployments some time. Shouldn't be a biggie, but worthwhile I reckon.

Just need to run `mvn clean install -Pitests` to run in Phantomjs, `mvn clean install -Pitests,chrome` to run in Chrome. Just one simple test right now - checking welcome page - but we can flesh out more & hopefully QE can help out too.

I'll update docs now so please don't merge before I've added that.