[skip ci] working on gtest landmark

schema/state/StateO2d.schema

 value:
   _type: Vector1d
-  _mandatory: false
+  _mandatory: true
   _doc: A vector containing the orientation, yaw [rad].
 
 prior:

schema/state/StateO3d.schema

 value:
   _type: Vector4d
-  _mandatory: false
+  _mandatory: true
   _doc: A vector containing the quaternion values (x, y, z, w)
 
 prior:

schema/state/StateP3d.schema

 value:
   _type: Vector3d
-  _mandatory: false
+  _mandatory: true
   _doc: A vector containing the position (x, y, z) [m].
 
 prior:

schema/state/StateV3d.schema

 value:
   _type: Vector3d
-  _mandatory: false
+  _mandatory: true
   _doc: A vector containing the velocity (x, y, z) [m/s].
 
 prior:

test/CMakeLists.txt

@@ -82,6 +82,8 @@ wolf_add_gtest(gtest_frame_base gtest_frame_base.cpp)
 # GraphSearch class test
 wolf_add_gtest(gtest_graph_search gtest_graph_search.cpp)
 
+# Landmark classes test
+wolf_add_gtest(gtest_landmark gtest_landmark.cpp)
 
 # LocalParametrizationXxx classes test
 wolf_add_gtest(gtest_loader gtest_loader.cpp)