Shell: Added PersistentData and updating menu with found servers
libdeng2: Improved Beacon to include server's listening port in message

This allows Beacon to identify a server fully at the lowest level.
libshell: Improved ServerFinder for continuous operation

The finder is now started automatically after construction. Old entries
expire if nothing is heard from the server. ServerFinder will also
parse the contents of the Beacon's message (which contains a Record).
libdeng2|Fixed: Bug in changing the values of ConstantRule

Setting the value twice could lead to the second time being ignored.
libdeng1: Lowered log level of garbage recycling messages

The announcement about recycled allocations/instances is now at the
lowest (trace) level.