single click file upload

enable "single click upload" of a single file on several components inside the Moodle framework.

in general, i gave the upload FORM a name : "upload"
and added a javascript onchange event to the input file(type)
that calls the submit function of the current FORM.

changes are in the following components:
files (repository)
assignment (upload)
assignment (uploadsingle)

i have also made a special usability shortcut inside the Files page
in which i included the "single upload file to the current folder" function
at the end of the main Files page.
(no need to click the old "upload file" and navigate to a new page)

hope you like it and that it does not break anything

btw,
i was inspired by this tracker to try and patch moodle to have a single click file upload.