Indentation script for R

Summary:
This is a javascript indentation script for the statistical language R. This script is for all software using KTextEditor (e.g. Kate), but more specifically for RKWard, which is an IDE for R.

I tested it for corner cases for some time so it should be quite robust, although my ability to find corner cases alone is obviously limited by a lack of diversity in coding styles.

Reviewers: KTextEditor, RKWard, cullmann

Reviewed By: KTextEditor, cullmann

Subscribers: kwrite-devel, kde-frameworks-devel, cullmann, tfry, dhaumann

Tags: Kate, Frameworks

Differential Revision: https://phabricator.kde.org/D12587