DS-1994: Use HTML5 to upload files in Submission Process of JSPUI.
Use html5 upload only if supported by the browser. Fallback is default.

The old upload should be the default upload. HTML5 upload should be used
only if it is supported by the browser. This commits repairs the use of
the old upload and makes it the default.

A severe bug was found and fixed by this commit: The first version of
this feature was not thread safe as it used a instance variable were it
shouldn't. This commit fixes this bad behavior.

The message to inform the user, that its browser does not support
enhanced upload can be translated now.
Merge pull request #551 from tuub/DS-1994

DS-1994: Use HTML5 to upload files in Submission Process of JSPUI.