mouse: add title to header bar

The header bar of the mouse panel can display a title, when the stack only contains the mouse and the touchscreen subpanel.

This header bar, however, does not inherit the title widget from the common CcPanel, as it contains the view switcher.

It is needed to add the correct title as a property to the switcher to let it display this title, if no switcher is.

This title is to be there according to the design mock-ups.

before	after