add 'determine uncancelled' to 'on player clicks'

A lot of click events seem to be cancelled by default... this adds a
determination for 'uncancelled' in the click event.
Actual usage: right-clicking a dragoncontrolstaff item while riding an
enderdragon:
normally, does nothing due to arbitrarily pre-cancellation (At least on
C-K's server)... but with a 'determine uncancelled' in the event,
right-clicking will properly cause the dragon to move downward.
I imagine plugins will cancel a lot of events that Denizen users want to
not be cancelled... so I think this should be the first of many
'uncancelled' determine options.

src/main/java/net/aufdemrand/denizen/scripts/commands/CommandRegistry.java

@@ -1596,7 +1596,7 @@ public void registerCoreMembers() {
 
         // <--[command]
         // @Name Push
-        // @Syntax push [<entity>|...] (origin:<entity>/<location>) (destination:<location>) (speed:<#.#>) (<duration>) (<script>)
+        // @Syntax push [<entity>|...] (origin:<entity>/<location>) (destination:<location>) (speed:<#.#>) (duration:<duration>) (<script>)
         // @Required 1
         // @Stable mostly
         // @Short Pushes entities through the air in a straight line.

src/main/java/net/aufdemrand/denizen/scripts/containers/core/WorldScriptHelper.java

@@ -3495,6 +3495,7 @@ public void playerGameModeChange(PlayerGameModeChangeEvent event) {
     //
     // @Determine
     // "CANCELLED" to stop the click from happening.
+    // "UNCANCELLED" to ensure other plugins will process the event properly.
     //
     // -->
     @EventHandler
@@ -3565,10 +3566,12 @@ else if (action == Action.RIGHT_CLICK_AIR || action == Action.RIGHT_CLICK_BLOCK)
 
         }
 
-        String determination = doEvents(events, null, event.getPlayer(), context, true);
+        String determination = doEvents(events, null, event.getPlayer(), context, true).toUpperCase();
 
-        if (determination.toUpperCase().startsWith("CANCELLED"))
+        if (determination.startsWith("CANCELLED"))
             event.setCancelled(true);
+        else if (determination.startsWith("UNCANCELLED"))
+            event.setCancelled(false);
     }
 
     // <--[event]