fix minor issues & cleanup

common/src/main/java/com/dfsek/terra/generation/MasterChunkGenerator.java

@@ -221,4 +221,8 @@ public class MasterChunkGenerator implements TerraChunkGenerator {
             }
         }
     }
+
+    public SamplerCache getCache() {
+        return cache;
+    }
 }

common/src/main/java/com/dfsek/terra/generation/math/SamplerCache.java

@@ -27,6 +27,9 @@ public class SamplerCache {
         return containerMap.computeIfAbsent(world.getSeed(), seed -> new Container(world)).getChunk(chunkX, chunkZ);
     }
 
+    public void clear() {
+        containerMap.clear();
+    }
 
     private class Container {
         private final World world;