Zotero icon should be a draggable target in the dock (or similar)

[stakats]

Dragged files (PDF, RIS, etc.) should be able to be dropped on the Zotero icon (in the OS X dock, Windows and Linux equivalents if possible) to create new items.

[dstillman]

Clarification:

PDFs and similar should create new items, equivalent to dragging files into the current collection.

RIS and similar should trigger an import prompt, equivalent to launching the file from the OS via Zotero. As noted by @simonster, this already works.