Modify structure of Swagger specs

[isaacvr]

Feature description

Add models definitions sections in Swagger spec.

Is your feature request related to a problem? Please describe.
Swagger spec for Skycoin node only defines inline responses. This leads to generation errors , e.g. in qt ( simelo/libskycoin-cpp#1 ) and tizen ( simelo/libskycoin-cpp#2 ) client libraries.

Describe the solution you'd like
All models in models definitions section. Add type field for operation items . Use $ref for array types links for type definition.

Describe alternatives you've considered
The inline response body does not work quite well for generators relying on some language / framework combinations .

Additional context
The structure is inspired on Pet app Swagger spec's models section . This layout works fine with many generators.