Move e2e tests to cucumber

[tonowie]

Cucumber offers simple way to describe tests, avoid boilerplate and share test scenarios across SDKs. So lets move to it!

Alvin has forked nemtechs project with e2e tests so we can build atop of that: https://github.com/proximax-storage/nem2-e2e-tests

For the time being I will create copy of the tests and slowly roll-out tests as they are implemented and working. Once current e2e tests are covered by cucumber I will drop them.

[tonowie]

OH and lets use groovy for the tests. it is good opportunity to ensure that API is good for groovy developers as stuff looks a bit different through the groovy lens