Project is in a runnable state again.

- The com.bradsbytes prefix was removed from all packages; the project now
  resides directly in the 'unmm' package.
- Marker has been removed. Its function was superfluous since TmxObject
  now does everything it was supposed to do.
- Spawner has been removed. The behavior of spawning is being moved into
  TmxObject and some combination of the TmxMap and Boundary classes. (This
  is unfinished at the moment.)
- Boundary: Instead of a 'markers' group, each boundary now has two
  groups; one called 'despawners' and one called 'respawners'. TmxObjects
  now add these to
- The items of TmxMap.groups have been merged back into TmxMap itself
  using plural versions of the names previously used in the groups
  property.
- TmxMap.namedGroups is now called 'groups'
- The 'exobjects' and 'entities' groups have been removed completely
  because they no longer serve an obvious purpose.