tutorials/multiphase/multiphaseEulerFoam: Multiphase blending changes

Updated tutorials for the changes to the blending system. Cases using
"none" blending have been updated to use "continuous" or "segregated" as
appropriate.

The bed tutorial has been extended to include a proper switch to a bed
drag model (AttouFerschneider) when the solid phase displaces the
fluids. This change made the trickleBed case a subset of the bed case,
so the trickleBed has been removed.

tutorials/multiphase/multiphaseEulerFoam/RAS/LBend/constant/phaseProperties

@@ -45,8 +45,8 @@ blending
 {
     default
     {
-        type            none;
-        continuousPhase gas;
+        type            continuous;
+        phase           gas;
     }
 }