Add Model generation support for the swagger writer.

[eawagner]

With the update to swagger 1.2, there are a few more changes that apply to models and all data types.

They have broken several common data types into two pieces; type and format. For example long is now 'integer' and 'int64' respectively.

Currently swagger-ui works with the old formats, even though there are a few bugs to give it away. These issues may need to be addressed when doing model generation.