Release 1.9.0 rc.1

DO NOT MERGE. Still waiting on some final tickets before this should go in.

I managed to get the changelog script modified to handle contributors and multiple parallel release branches.

This is an example of me walking through the steps outlined in https://github.com/ewinslow/Elgg/commit/292bac5451e286f3bc5b30162aaeafd3702cdb13

Comments appreciated