Rename settings and allow more flexible configuration by allowing the user to
enable click handlers for the tags and the layout label separately.
Add a scroll handler for the layout label so the user can scroll through the
available layouts. Enabling layout-scroll-wrap allows wrapping back to the
beginning/end of the array of available layouts.
next_layout and prev_layout take the address of a layout and returns the
next/previous layout in the m_layouts array if possible, wrapping if specified,
otherwise returns the same layout. This is used to for the layout scroll
handlers to cycle through layouts.
a22b2ffcc3