Fix random walking behavior.
More dudes and variableize some world size things.
Some bug fixes and add player-controller walker.
Refactor WalkingBehavior and formalize ID generation in Game19.
Center scene on player in Game19 ServerClientDemo.
Rudementary line-of-sight calculations in Game19.
Fixed player's step interval.
Improve rendering in Game19.
Remove that visible/invisible stuff from WalkingBehavior.
Refactor object identification/addressing.

Longs formerly known as 'IDs' are now called 'bit addresses',
which may (and do, in Game19's case) contain both flags and
instance identification.

Game19 blocks now know their own address.
Their behavior may handle messages for additional addresses.

Objects that have or contain other objects with and that track the
minimum and maximum bit addresses now implement BitAddressRange.
BitAddressUtil (formerly IDUtil) accepts these as arguments to
some functions that otherwise take a pair of longs.

Some convenience functions now accept an int ID as an alternative
to an address range.