Fixing release notes for upcoming 0.9.13 release

I hope I didn't miss anyone.
Notes:
- "Fix per-host replication" in carbon was reverted, so, removed from notes.
- Giving kudos for @favoretti for initial hack which lead to "Bulk-fetch metrics from remote hosts".

In progress: we need  to decide what to do with PR https://github.com/graphite-project/carbon/pull/240 (yep, it's from carbon because of wrong issue but really belongs to graphite-web) and #1026 IMO.
And :ship: it ASAP. :smile_cat: