Beautifier: Add option to use .clang-format file if present

The Beautifier Plugin made by Lorenz Haas lacks the possibility to use project defined .clang-format files. But this is standard in software engineering groups, where everyone has to use the same format. The format is normally defined by a .clang-format file distributed over scm with the project configuration.

Currently it is required to distribute the configuration manually, resulting in several distinkt configurations.