Implement additional Region data access operations.

Implement Region.invalidate(key).

Implement Region.remove(key).

Re-implement Region.get(key), Region.getEntry(key) and Region.put(key) to handle invalidated keys (Region entries).

spring-data-geode-test/src/test/java/org/springframework/data/gemfire/MockClientCacheApplicationIntegrationTests.java

@@ -89,6 +89,14 @@ public class MockClientCacheApplicationIntegrationTests {
     assertThat(this.example.getName()).isEqualTo("Example");
     assertThat(this.example.put(1, "test")).isNull();
     assertThat(this.example.get(1)).isEqualTo("test");
+    assertThat(this.example.containsKey(1)).isTrue();
+
+    this.example.invalidate(1);
+
+    assertThat(this.example.containsKey(1)).isTrue();
+    assertThat(this.example.get(1)).isNull();
+    assertThat(this.example.remove(1)).isNull();
+    assertThat(this.example.containsKey(1)).isFalse();
   }
 
   @ClientCacheApplication