Added bunch of javadocs and restricted some visibility.

No functional changes

src/main/java/org/scribe/model/OAuthConfig.java

@@ -1,5 +1,10 @@
 package org.scribe.model;
 
+/**
+ * Parameter object that groups OAuth config values
+ * 
+ * @author Pablo Fernandez
+ */
 public class OAuthConfig
 {
   private String apiKey;