Update FileDocumentViewer.js

added crsftoken for Mendix 4.0
added time in url to force refresh of iframe.
cleaned up code (functions also declared as variable)
Improved test for new object (Name instead of FileID)
jslint tested

Not compatible with Mendix 5.x yet.
Merge pull request #1 from ChrisdeG/master

Update FileDocumentViewer.js