QmlDesigner.ImportManager: Add special combobox

Combobox is styled and always shows "Add Import" as current text.
I reimplented the paint event to get this behavior.

Change-Id: I4448644397e7a39488f2e961728ebef924eec7ff
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
Debugger: Don't recreate gdb dumper object every time

This allows for easier caching of "expensive" information.

Change-Id: I97f272c795483250bd00a0ff899cb8c27b0ab6e9
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: hjk <hjk121@nokiamail.com>
QmlDesigner.ImportManager: Adding proper icon to label

Change-Id: I7caf53091dae99239db2cc59c0a067b9d77fc1c9
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>