QmlDesigner: Make Enumeration::nameToString const

Change-Id: I311bb1eb0d6511c1e6ef787d2f28eed0d777480c
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>
QmlDesigner: Support enumerations for aliases

Task-number: QTCREATORBUG-12229
Change-Id: I36632cdcf16a2d391b653be71f2df58cb8814a21
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>