Adapt /images calls to handle additional media types

[bellerbrock]

It seems there is no good way in the current BrAPI spec for Field Book to submit audio recordings to a BrAPI server. Broadening the images endpoints to other media types could solve the problem, and could be useful for other media types like video as well.

[kamathprasad9]

The digital phenotyping project aimed at combining audio files along with the Field Book's GeoNav log files and storing them on Breedbase via BrAPI. Currently we are trying to send a zip file containing the files that we want. As there is no direct support for non-image files, we are uploading the base64 contents on the POST /images endpoint. If we could have support for different media types, that would indeed by very useful.

[BrapiCoordinatorSelby]

related to #604