Move the testsuite classes back to src/test
Do not deploy the testsuite
Fix a bug where HttpObjectDecoder produces LastHttpContent after entering BAD_MESSAGE state

- Fixes #2103
- Added LastHttpContent.EMPTY_LAST_CONTENT.toString() for athestic reasons.
Allow to extend the provided tests by the testsuite

This allows custom transport implementations to just re-use the tests provided by netty and so make sure everything works like expected.
Merge remote-tracking branch: upstream/master