[clang-format] Reorganize RawStringFormat based on language

Summary:
This patch changes the structure for raw string formatting options by making it
language based (enumerate delimiters per language) as opposed to delimiter-based
(specify the language for a delimiter). The raw string formatting now uses an
appropriate style from the .clang-format file, if exists.

Reviewers: bkramer

Reviewed By: bkramer

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D42098

llvm-svn: 322634