Introduce new Beautifier plug-in

Beautifier is a plug-in for source code beautifiers.
Currently Artistic Style, Clang-format and Uncrustify are supported.

Task-number: QTCREATORBUG-7489
Change-Id: I8dde9a8ba6a6a55537bfd450ec82ef966ed283c0
Reviewed-by: David Schulz <david.schulz@digia.com>