Fix for 992.

Move WS into its own Scala and Play modules and add documentation.
Fix specs to include tests, rename play-ws-java to play-java-ws.
Add tests to verify that the WSPlugin loads correctly.
Add commons-codec
Unwrap ExecutionException in handleError (e.g. to enable AssertionError to be displayed)
Make scalariform happy
Remove spurious WS import.
Merge pull request #1944 from char101/patch-1

Unwrap ExecutionException in handleError (e.g. to enable AssertionError to be displayed)
Merge pull request #992 from wsargent/992-play-ws

Pull WS API out of play core
[#1911] Use queryString in WS@java
Don't use httpbin.org
Fix parsing of querystring and user:password
Use provided url