Fix variance problems.
Fix variance problem in quick fix test.
Added DiagnosticFactoryToRendererMap.put(Renderers.MultiRenderer)
Create AbstractDiagnosticWithParametersRenderer with renderParameters method.
Add support for check diagnostic parameters in test.
Added @NotNull
Add TypeBinding.
Create VarianceChecker.
Added VarianceChecker to TopDownAnalyzer.
Added Variance tests
Add variance check for class supertypes.