ETCH-276 Added typedef for SmartPointer of EtchNumber

Change-Id: Iaff6a6ab87ac824f4d60bdb3d405b39d329900d9

git-svn-id: https://svn.apache.org/repos/asf/etch/trunk@1547310 13f79535-47bb-0310-9956-ffa450edef68