Allow for file uploads

[kellyjandrews]

The equivalent of this need to be available:

curl -X POST \
-H "Content-type: multipart/form-data" \
-H "X-API-KEY: API_KEY" \
-F "file=@PATH_TO_FILE" \
"https://api.syncano.io/v1/instances/instance_name/classes/class_name/objects/"

Could be a header override, or a specific method which abstracts Content-type: multipart/form-data.

[dancio]

this is already solved