[Qgis-developer] Visual changelog for 2.6

[Nyall Dawson]

Hi all,

I just trawled through the git commit log and copied all the new
features I could find to the visual changelog for 2.6. I've done it
very roughly, mostly just bullet points (that's all I've got time for
at the moment), so it would be appreciated if someone could flesh out
these entries and add screenshots, etc.

Some notes:
- Sorry if I've missed any features - it's kind of hard to tell from a
commit sometimes exactly what was added/changed
- I've left off all processing related commits as there was just too
many of them to check through. Hopefully someone more familiar with
processing can add these.
- I ran into a bug with the changelog site were there's a fixed limit
to the number of "pending" entries shown. So I had to approve a bunch
of unfinished entries to be able to properly edit these missing
pending entries. Sorry if this makes things harder to review, I had no
choice...

The new features list is HUGE. Nice work everyone :)

Nyall