Move api classes to yadc/core/models
Namespace core classes
Use Yadc::Core namespace in engine code
Require core classes with a single file
Yadc::Core::Direction is now an extension
Pathfinder becomes a Core extension
Move engine code to yadc/engine
Namespace Engine classes
Move remaining extensions to Yadc::Engine
Base core class of movement skill is now overridden by engine
Yard::Core::Character::Action is brought by engine
Remove I18n dependency
Distribute dependencies to Core and Engine
Merge pull request #100 from rafaelgonzalez/new-namespaces

Separate Core and Engine related classes