add comments explaining naming quirks for sip

Author: Doug Black

src/main/java/com/twilio/sdk/resource/instance/sip/CredentialListInstance.java

@@ -14,7 +14,13 @@
 import com.twilio.sdk.resource.instance.sip.Credential;
 import com.twilio.sdk.resource.list.sip.CredentialList;
 
-
+/**
+ * This class is the instance resource corresponding to /CredentialLists/CLXXX.
+ *
+ * NOTE: The 'Instance' suffix in the name was added to avoid a name clash with the list resource
+ * that corresponds to /Credentials. This unfortunate quirk is caused by this library's convention of
+ * appending 'List' to instance resources to form their list counterpart.
+ */
 public class CredentialListInstance extends InstanceResource {
 
 	/** The Constant SID_PROPERTY. */
@@ -30,7 +36,7 @@ public CredentialListInstance(TwilioRestClient client) {
 	}
 
 	/**
-	 * Instantiates a new CredentialList.
+	 * Instantiates a new CredentialListInstance.
 	 *
 	 * @param client the client
 	 * @param sid the sid

src/main/java/com/twilio/sdk/resource/list/sip/IpAccessControlListList.java

@@ -11,6 +11,11 @@
 import com.twilio.sdk.resource.instance.sip.IpAccessControlList;
 import org.apache.http.NameValuePair;
 
+/**
+ * This class is a list of IpAccessControlLists.
+ * While the name may seem odd at first, it actually is a list of lists,
+ * so the name is correct.
+ */
 public class IpAccessControlListList extends ListResource<IpAccessControlList> implements IpAccessControlListFactory {
 
 	/**