New developer documentation

[Matt Zimmerman]

Colin and I have put together a new landing page for developer
documentation, to supersede DeveloperResources and some other incomplete or
outdated documentation:

https://wiki.ubuntu.com/UbuntuDevelopment

It's intended to provide a starting point for people who want to get
involved in development, as well as an index of relevant information for
active developers.  The table of contents should provide a good overview of
its intended scope.

I would appreciate feedback from developers about it, especially:

- Existing resources which should be linked from it, or incorporated into it

- Errors and inaccuracies

- Information which isn't currently documented anywhere, but should be

- Text for sections which haven't been written yet

If you're uncertain, ask before editing the document, but feel free to make
changes which are consistent with its purpose and scope.

-- 
 - mdz