* Add joystick type detection (with joystick_type setting to override it)
* Fix multiple joysticks from interfering with each other by only reading from one (add joystick_id setting)
* Add support for Xbox controllers
- Add warning log level
- Change debug_log_level setting to enumeration string
- Map Irrlicht log events to MT log events
- Encapsulate log_* functions and global variables into a class, Logger
- Unify dstream with standard logging mechanism
- Unify core.debug() with standard core.log() script API