Extended functionality of the DropZone widget
- 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.
- bumped version number to 5.10.1d35
