[Forward port 7.8] Xhina first soft enter (<br/>) is not working for Webkit browsers

Start with a Webkit browser, then try to insert new lines using soft enter: SHIFT+ENTER. The first one will never work, only the second one and further ones.

Cause: the keystroke handler is browser specific, and in the Webkit.js the soft enter is not handled at all:

case 13: // ENTER
if( ev.shiftKey )

{ //TODO: here we need to add insert new line }

This should be handled by paraHandlerBest.js plugin which is taking take care of this for other browsers (the plugin is bound at runtime to the outwardhtml method).

To reproduce:

• Open a document with a Xinha field
• In the Xinha field type "First line", then press Shift+Enter, then "Second line", then Shift+Enter again, then "Third line"
• Click "Save"
  Expected result: The above inputs are indeed on separate lines
  Actual result: The first line is "First lineSecond line"