Update Kinyarwanda

* The native name is a bit different from the English one.
* Since nothing is using the slug, change it to the three-letter code.


git-svn-id: https://glotpress.svn.wordpress.org/trunk@990 ac016dd8-9c08-41e1-ba26-5f12ba476432
Remove remainng RRC-format-related files

Props markoheijnen


git-svn-id: https://glotpress.svn.wordpress.org/trunk@991 ac016dd8-9c08-41e1-ba26-5f12ba476432