sparse module:

- remove some useless stuff => let's focus on a single sparse matrix format
 - finalize the new RandomSetter

cmake/FindGoogleHash.cmake

@@ -0,0 +1,16 @@
+
+if (GOOGLEHASH_INCLUDES AND GOOGLEHASH_LIBRARIES)
+  set(GOOGLEHASH_FIND_QUIETLY TRUE)
+endif (GOOGLEHASH_INCLUDES AND GOOGLEHASH_LIBRARIES)
+
+find_path(GOOGLEHASH_INCLUDES
+  NAMES
+  google/dense_hash_map
+  PATHS
+  ${INCLUDE_INSTALL_DIR}
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(GOOGLEHASH DEFAULT_MSG GOOGLEHASH_INCLUDES)
+
+mark_as_advanced(GOOGLEHASH_INCLUDES)