Adds @odata.count parameter to collection responses

[irvinesunday]

Fixes #196

This PR:

• Adds an @odata.count as a pagination property for collection responses. Together with @odata.nextLink these are componentized and reused.
• Adds a new setting Settings.EnableCount which controls whether to set the @odata.count.
• When Settings.EnablePagination and Settings.EnableCount are enabled, these properties alongside the base properties of a type are appended to an allOf schema.
• Updates test.

When Settings.EnablePagination = true and Settings.EnableCount = true the new schema for collections would look like:

And the BaseCollectionPaginationCountResponse schema:

And the BaseCollectionCountResponse schema:

[baywet]

Thanks for making the changes, I pushed a much simpler implementation :)