Write a new make format target that does applies clang-format in areas that make sense; intended to be run before committing or sending patches. Eventually this command could also be run on the continuous build server.

This command should:

• Check the clang-format version to ensure it is >= 6.0.
• Run clang-format on portions of the code where it makes sense. To start (this task) just do intern/, but not libmv or other areas that shouldn't get updated.
• This should be done before the "big migration".
• This includes weeding the .clang-format file to make sure it's what we've broadly agreed upon.
• This includes updating .editconfig to use spaces (or any other lingering IDE config files that are lying around).