Added different sub interface for prevent double definition in IFile.

If we implement IMime directly in IFile, we get the fields contentType and encoding twice.
One time in the Mime object wich is a subobject rendered in a separate widget and one time
in the IFile obeject itself.

TODO: check Schema wwidget, there is still a bug in the fileupload form.
Could be a proxy error.

browser/schemawidgets.py

@@ -114,29 +114,16 @@ def getInputValue(self):
         return content
 
     def applyChanges(self, content):
-        print ""
-        print "applyChanges"
         field = self.context
-        print "field = self.context ", self.context
-        print "content ", content
 
         # create our new object value
         value = field.query(content, None)
-        print "value ", value
         if value is None:
             # TODO: ObjectCreatedEvent here would be nice
-            print "if value is None:"
             value = self.factory()
-            print "value ", value
 
         # apply sub changes, see if there *are* any changes
         # TODO: ObjectModifiedEvent here would be nice
-        print "self ", self
-        print "isProxy(self) ", isProxy(self)
-        print "isProxy(value) ", isProxy(value)
-        print "isProxy(field) ", isProxy(field)
-        print "isProxy(content) ", isProxy(content)
-        print "self.names ", self.names
         changes = applyWidgetsChanges(self, field.schema, target=value,
                                       names=self.names)