Fix db.queryExecuteTimeLimit doc
Use URI instead of URL to parse Java WS URLs

AsyncHttpClient eventually passes the url to URI.create anyway, so this
means that NingWSRequestHolder will fail in a manner consistent with
AsyncHttpClient.

The specific use case that this has been done to address is allowing
WebSocket URLs, which URI.create is fine with, but new URL throws an
exception.
Clean up various compile warnings
Workaround internal deprecation warnings
Clean up test:compile warnings
Merge pull request #3323 from pvlugter/warnings

Clean up warnings
Merge pull request #3349 from jroper/ning-uri-create

Use URI instead of URL to parse Java WS URLs
Merge pull request #3232 from yokomizor/fix_db_queryExecuteTimeLimit_doc

Fix db.queryExecuteTimeLimit doc
Reinstating disabled WebSocket test

Fixes #2729