Moved Proposal model from wiki to source code and updated ProposalModel wiki page.
Moved Proposal model from wiki to source code and updated ProposalModel wiki page.

Patch by: Pawel Solyga
Review by: Todd Larsen
Review issue: 362
Review URL: http://codereviews.googleopensourceprograms.com/362

MatthewWilkes/mw4068-packaging,MatthewWilkes/mw4068-packaging,MatthewWilkes/mw4068-packaging,MatthewWilkes/mw4068-packaging