[CB-2963] Re-enable sending messages in batches.

Disabled by CB-1745, which is now reverted.
[CB-2202] Remove Plugin.java (was deprecated).
Fixing URL transformation algorithm

It didn't work with URL like this:
http://host.com/path/to/file.txt#/foo?bar=baz
When hash sign is in front of question mark - it only strips the question mark, leaving the hash and breaking the whole app.