Addition of a fixed canvas layout able to freely position and resize widgets
over a background. Can be used for floorplans or schemas (as an alternative
to floorplan pages), with the controls rendered over the image.
Rework layout type selection - default to responsive - and allow to select
a fixed type layout when the page is empty.
Signed-off-by: Gautier Taravella <tarag@mailbox.org>
Also-off-by: Yannick Schaus <github@schaus.net>
Gautier