This change adds support for the full screen handwriting input.

In full screen handwriting input, the user is able to use the
whole application screen as a container for handwriting input.

This feature is available to those application integrations,
which integrate the new HandwritingInputPanel type to the
application QML. The HandwritingInputPanel works as an add-on
to the existing InputPanel, so it cannot be used exclusively
without the InputPanel.

Change-Id: I11530b9ccbc66aa59b210bec94d7bb87f0826370
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>