Support media types other than json

Created by: bodograumann

Currently the new typescript generator only supports receiving http responses with Content-Type: application/json. This is an approach to support other media types as well. In particular the first goal is to allow parsing arbitrary binary files as HttpFile. Later other media types, like xml could be added (possibly togglable with an config option to not always pull in the relevant parser library)

Please have a look, when you find the time @TiFu. The file download is not quite finished though.

Cf. #802 (closed)