[BUGFIX] Flash uploader doesn't work in Filelist clickmenus

The Flash uploader only works in the click menu of the folder tree in
the Filelist module. It doesn't work in
- the click menu of a folder in the "right frame"
- the click menu in a folder (in the right top)
This is because the Flash uploader JS is only observing a click event
to a button but cannot be called directly.

Change-Id: I6da96f76a12d305e198b2db53c6009b6c9c1d13b
Resolves: #21288
Releases: 6.0, 4.7, 4.5
Reviewed-on: https://review.typo3.org/19211
Reviewed-by: Henrik Ziegenhain
Tested-by: Henrik Ziegenhain
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn