* No more access to the singleton instance from everywhere (RenderingEngine::get_instance dropped)
* RenderingEngine::get_timer_time is now non static
* RenderingEngine::draw_menu_scene is now non static
* RenderingEngine::draw_scene is now non static
* RenderingEngine::{initialize,finalize} are now non static
* RenderingEngine::run is now non static
* RenderingEngine::getWindowSize now have a static helper. It was mandatory to hide the global get_instance access
* Various code style fixes
* Use range based for loops
* Use empty instead of empty objects
* Use C++11 default keyword for trivial constructors and destructors
* Drop some useless casts
* Use emplace_back instead of push_back to improve performance of some vectors push
* Add Device3D class which will contain IrrlichtDevice interface
move getSupportedVideoDrivers to Device3D
Add Device3D singleton & use it in various places
Rename Device3D to Rendering engine & add helper functions to various device pointers
More singleton work
RenderingEngine owns draw_load_screen
move draw functions to RenderingEngine
Reduce IrrlichtDevice exposure and guienvironment
RenderingEngine: Expose get_timer_time() to remove device from guiEngine
Make irrlichtdevice & scene manager less exposed
* Code style fixes
* Move porting::getVideoDriverName, getVideoDriverFriendlyName, getDisplayDensity, getDisplaySize to RenderingEngine
Fix XORG_USED macro -> RenderingEngine + create_engine_device from RenderingEngine constructor directly
* enum paralax => enum parallax
* 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
