Remove all references to old CGrid system (#672)

* add overload to ActionManager to support capturing an AZStd::function

* move snapping settings to new settings registry

* remove unneeded reference in ViewportSettings

* move viewport setting function implementations to .cpp file

* add more sensible default values for snapping

* fix variable name for angle snapping

* remove const from function prototype value parameters

* add import/export api for free functions

* change from std::bind to a lambda

* remove redundant const for constexpr string_view

* add AZStd alias for std::abs

* restore grid and angle snapping

* add overload to ActionManager to support capturing an AZStd::function

* remove old legacy CGrid code

* fix build after merge

* review feedback changes - remove 1.0f multiplies

Code/Sandbox/Editor/Objects/SelectionGroup.cpp

@@ -342,7 +342,8 @@ void CSelectionGroup::Rotate(const Matrix34& rotateTM, int referenceCoordSys)
 
         if (referenceCoordSys == COORDS_USERDEFINED)
         {
-            Matrix34 userTM = GetIEditor()->GetViewManager()->GetGrid()->GetMatrix();
+            Matrix34 userTM;
+            userTM.SetIdentity();
             Matrix34 invUserTM = userTM.GetInvertedFast();
 
             ToOrigin = invUserTM * ToOrigin;