Open API interface to layouts.
The routines in this file pertains to
. Create a view in a layout.
. Read/set view borders in a layout.
. Replace a view in a layout.
. Read the current layout name and work view name.
. Save the current layout.
. Retrieve/delete/rename a layout.
. Cycle layouts in a part.
. Read the number of views in a layout.
. Cycle views in a layout.