Add design principles for the project

These are the principles initially brainstormed and captured by @mlandauer , @henare and @equivalentideas at the design kickoff workshop 2014-08-18.
Change 'Government' to 'government'

https://github.com/openaustralia/publicwhip/pull/282#issuecomment-52582746
Merge pull request #282 from openaustralia/design-principles

Add design principles for the project