Split rest request binding parameters into a separate file from the mechanics of their use
copy the HTTP request header into the RestRequest
added ability to emplace() with arguments
added JsonPromise class in which we pass around immutable JSON
respect JSON's rules to not put NaN or Inf into JSON; write them as strings instead
Merge branch 'datacratic-internal-branch-2' of github.com:datacratic/soa into datacratic-internal-branch-2