Accessibility: add focus action

This at least implements the focus action for items with activeFocusOnTab
which works with most controls. VoiceOver for example uses this action.

Task-number: QTBUG-38870
Change-Id: I3bdaacec6b07e9baf020499e2e4826e42fe316f0
Reviewed-by: Jan Arve Sæther <jan-arve.saether@digia.com>
TextEdit: fix cursor rectangle positioning

QQuickTextControl::cursorRectangleChanged() wasn't emitted as
appropriate when dragging mouse => The cursor delegate was stuck
in wrong position under certain circumstances, especially when
selecting multiple lines.

Task-number: QTBUG-38947
Change-Id: Ib5b0d2f6ea2a1b3712fbaba4a7ad1865d2b0a74e
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>