Macros: Clean up singleton APIs

Task-number: QTCREATORBUG-9763

Change-Id: I76c4d60279f738272b0cf5fda651ce266f798c2c
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Perforce: singleton cleanup

Task-number: QTCREATORBUG-9763

Change-Id: I8dbf3c1e5b7e1bea525123bf02a7e9952c94abe2
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
QmlDesigner: moving CrumbleBar and ComponentAction

Moving the CrumbleBar and the ComponentAction out of the FormEditor
into the DesignModeWidget.

These widgets are about document navigation and do not belong to
the FormEditor.

Change-Id: I5cd177d70f7c8f9cc2913c8c3c640d62fefd718d
Reviewed-by: Marco Bubke <marco.bubke@digia.com>
QmlDesigner.Model: adding isComponent to ModelNode

This function checks if the ModelNode is a Component or has a delegate
which is a Component.

Change-Id: I6bc92c3246b58eb04a5d37722e821dbed52147e5
Reviewed-by: Marco Bubke <marco.bubke@digia.com>