[Copy-Paste][ModelExplorer][UML] The UML references are not well udpated by the copy/paste

Issue reported from Papyrus-Classic org.eclipse.papyrus-classic#16

When a UML Stereotype defined properties typed by UML Element or by Stereotype application, the values are not updated by the copy/paste process.

After the paste, the pasted element still reference the initial values and not the duplicated one.