Distribute also takes relative - although this is about to be undone.
Correction to relative/absolute coordinates when layouting.

It is now the clients role to provide the correct bounds (relative or
absolute) to the layout operations.
Moved layout sizing into its own operation
Layout operations are now prefixed with 'Layout'
Constraints of a layoutee are now removed when the layoutee is removed from its parent.
Some minor code standard fixes in gxViewElement and gxVisual
SetBounds now accounts for invisible elements.