[fixes #2849] Make ToString's onlyExplicitlyIncluded a config key.

test/transform/resource/after-ecj/ToStringExplicitIncludeConf.java

@@ -0,0 +1,10 @@
+@lombok.ToString class ToStringExplicitIncludeConf {
+  int x;
+  @lombok.ToString.Include int y;
+  ToStringExplicitIncludeConf() {
+    super();
+  }
+  public @java.lang.Override @java.lang.SuppressWarnings("all") java.lang.String toString() {
+    return (("ToStringExplicitIncludeConf(y=" + this.y) + ")");
+  }
+}