- added parameters "label", "disposition" and "file_name_prefix" for better configurability
- added support for updating the current page with feedback of the dropped files. This is used e.g. by the online exam in the exam protocol to display incrementally thumbnails of feedback files.
- change property "uploader" to "disposition", since "uploader" is somewhat ambiguous. "Disposition" defines, what happens after the file was uploaded, e.g. whether the content has to be transformed, etc.
I am not fully happy with the handlings of "return_url" in exam workflows. Maybe this can be reworked in a way such that "local_return_url" is not neccsessary in the future.