Tidy up presenters folder, such that all the actual node presenters (i.e. corresponding to an actual node) lives inside their own folder

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Presenters/MaterialGraphPresenter.cs

             typeMapper[typeof(RemapMasterNode)] = typeof(RemapMasterNodePresenter);
             typeMapper[typeof(MasterRemapInputNode)] = typeof(RemapInputNodePresenter);
             typeMapper[typeof(AbstractSubGraphIONode)] = typeof(SubgraphIONodePresenter);
-            typeMapper[typeof(AbstractSurfaceMasterNode)] = typeof(SurfaceMasterPresenter);
+            typeMapper[typeof(AbstractSurfaceMasterNode)] = typeof(SurfaceMasterNodePresenter);
             typeMapper[typeof(LevelsNode)] = typeof(LevelsNodePresenter);
             typeMapper[typeof(ConstantsNode)] = typeof(ConstantsNodePresenter);
             //typeMapper[typeof(SwizzleNode)] = typeof(SwizzleNodePresenter);

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Presenters/Nodes.meta

+fileFormatVersion: 2
+guid: 7e4695133ddd49cf97b1629ca5537e5b
+timeCreated: 1502981029