[INTERNAL] XMLComposite: Refactor to use existing functionality
[INTERNAL] XMLComposite: Refactor to use existing functionality

Note 1:
 - Removal of parseScalarType that s already in Utils
 - Use the observer

Note 2:
 - Tested with the old mdc table
 - need a global entry point to be prepared for retemplating 
 also on aggregations that are of invalidate mode "template" which 
 currently does not work

Change-Id: I8c58fc9dbb8218bdc0dfdbb36f9cddd0654b109e

SAP/openui5,cschuff/openui5,SAP/openui5,cschuff/openui5,SAP/openui5,cschuff/openui5,SAP/openui5