use default parameters if none provided, and remove gtsam namespace prefix in .h file

Author: johnwlambert

gtsam/sfm/ShonanAveraging.h

@@ -430,8 +430,8 @@ class GTSAM_EXPORT ShonanAveraging2 : public ShonanAveraging<2> {
                    const Parameters &parameters = Parameters());
   explicit ShonanAveraging2(std::string g2oFile,
                             const Parameters &parameters = Parameters());
-  ShonanAveraging2(const gtsam::BetweenFactorPose2s &factors,
-                   const gtsam::ShonanAveragingParameters2 &parameters);
+  ShonanAveraging2(const BetweenFactorPose2s &factors,
+                   const Parameters &parameters = Parameters());
 };
 
 class GTSAM_EXPORT ShonanAveraging3 : public ShonanAveraging<3> {