Bug 20969: (follow-up) Move focus to textarea whe modal is shown

Bug 20969: (follow-up) Move focus to textarea whe modal is shown

This follow-up adds code to move the mouse cursor to the modal window's
textarea when the modal is displayed.

To test, apply the patch and test the process of adding/editing notes on
an order. Confirm that the focus moves to the textarea when the note
editor modal window is shown.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Charles Farmer <charles.farmer@inLibro.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>