Set the Stage
Implement Actors logic on new DungeonLevelCharacter class

Deleted Dungeon::Level::Character subclasses & submodules, that code
structure may be used again sometime
Rework Character key bindings logic
Bring back camera movement controls
Display DungeonLevel
Remove save system

Will need to be reimplemented later when code structure is more definite
Merge pull request #39 from rafaelgonzalez/stage-actors-actions

Use Libgdx's Stage, Actor and Actions