This patch consists of:
-Add NetworkInterface to wrap objects bound to a stack and update
socket code to handle this in addition to NetworkStacks
-Update MeshInterface to inherit from NetworkInterface
-Update NanostackInterface so it only inherits from NetworkStack
-Add MeshInterfaceNanostack and update LoWPANNDInterface and
ThreadInterface to inherit from this
Bytes are stored by default, however enough space is allocated in
a SocketAddress to generate the string representation if necessary.
Currently there is no support for shortened addresses