Remove border from TreeMenu
Added a 3px border to contentPane panel.
Check if user defined TreeModel isn't null
Update buttons "enabled" property in asynchronous mode to work properly
when the Form mode is changed quickly.

Example:
form.executeUpdate();
form.setMode(Consts.EDIT);

Before this patch the form will be in EDIT mode but the buttons still
"enabled in READONLY mode", because the executeUpdate() method changes
the form mode to READONLY internally.

GenericButtons and LinkButtons maybe still have this problem.
Cleaning
Cleaning