try ceres 2.1.0

SuperBuild/cmake/External-Ceres.cmake

@@ -8,7 +8,7 @@ ExternalProject_Add(${_proj_name}
   STAMP_DIR         ${_SB_BINARY_DIR}/stamp
   #--Download step--------------
   DOWNLOAD_DIR      ${SB_DOWNLOAD_DIR}
-  URL               http://ceres-solver.org/ceres-solver-2.0.0.tar.gz
+  URL               http://ceres-solver.org/ceres-solver-2.1.0.tar.gz
   #--Update/Patch step----------
   UPDATE_COMMAND    ""
   #--Configure step-------------