added SignatureType and querystring signing functionallity

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

@@ -10,6 +10,7 @@ public class OAuthConfig
   private String apiKey;
   private String apiSecret;
   private String callback;
+  private SignatureType signatureType;
   
   public OAuthConfig(String key, String secret)
   {
@@ -52,4 +53,14 @@ public class OAuthConfig
   {
     this.callback = callback;
   }
+
+  public SignatureType getSignatureType()
+  {
+    return signatureType != null ? signatureType : SignatureType.Header;
+  }
+
+  public void setSignatureType(SignatureType type)
+  {
+    this.signatureType = type;
+  }
 }