Add support for property-placeholders in {{propertyName}} notation

[AlanFoster]

It would be good to support automatic completion/reference finding etc for the property placeholder notation

For example

   <to uri="{{propertyName}}" />

[AlanFoster]

Related to this, the cxfEndpoint can make use of this notation too within its attributes for instance

    <cxf:cxfEndpoint id="webservice" address="{{cxf.address}}" serviceClass="foo.bar.baz" />