rendering.components.layout: Initial infrastructure for the layout framework
rendering.components.layout: Initial infrastructure for the layout framework

Introduce generalized declarative layout framework.

Automatic UI generation from form definitions is obviously not perfect
for practical applications.  On the other hand, hardcoding layouts in
JavaScript is a road to nowhere.

Declarative UI markup is not new, of course, and our design is heavily
inspired by QML and friends.  The distinguishing feature of our approach
is tight integration with data schema and semantics utilizing well
established form reflection mechanisms.

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