Script context manager
Added ExecuteChecked method for ScriptContextHandle
Exported some of renderer interface to script
Merge branch 'master' of https://github.com/yvt/openspades

Conflicts:
	Sources/AngelScript/addons/scriptbuilder.h
	Sources/Core/Math.cpp
	Sources/ScriptBindings/ScriptManager.cpp
	Sources/ScriptBindings/ScriptManager.h
Merge and some refactor (ref-counting some objects)