install .dek packages by dragging them onto Pd

[umlaeute]

deken packages use the .dek extension, so they often won't be recognized as .zip-files.
(and even if they are recognized, zip wouldn't unzip them to the correct location on its own).

it would be cool, if we could extract deken files directly with Pd.

proposal 1

1. the user drags a .dek file onto the Find externals... window
2. the package is automatically extracted to the default location (as if the user clicked on the download link after a successful search)

proposal 2

1. the user can create a "file association" between .dek files and Pd-GUI.
2. double clicking the .dek file would open the GUI which would do the sensible thing (install it)

however, .dek should not be in the list of files to Open...