Add Movable Amethyst Rule (#894)

* Add Pushable Amethyst Rule

As discussed in #79 of ilmangos peaceful challenge. He said he'd do it, I figured I could beat him to the punch :)
https://youtu.be/0-fAKpr_J8k?t=1076

* Name change - movableAmethyst

Co-authored-by: hugeblank <hugeblank@gmail.com>

src/main/java/carpet/CarpetSettings.java

@@ -315,6 +315,9 @@ public class CarpetSettings
     )
     public static boolean hopperCounters = false;
 
+    @Rule( desc = "Allows Budding Amethyst blocks to be moved by pistons", category = FEATURE )
+    public static boolean movableAmethyst = false;
+
     @Rule( desc = "Guardians turn into Elder Guardian when struck by lightning", category = FEATURE )
     public static boolean renewableSponges = false;