WIP: Apriltag

MR open while Gitflow transition

It can stay open until big merge in the future

src/constraints/CMakeLists.txt

@@ -5,7 +5,11 @@ INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR})
 # Add in this section the CONDITIONAL CLUES [IF/ELSE]  
 # for external libraries and move inside them the respective lines from above.  
 
-
+IF (OPENCV_FOUND AND Apriltag_FOUND)
+  SET(HDRS_CONSTRAINT ${HDRS_CONSTRAINT}
+    ${CMAKE_CURRENT_SOURCE_DIR}/constraint_autodiff_apriltag.h
+      )
+ENDIF(OPENCV_FOUND AND Apriltag_FOUND)
 
 #=========================================
 #=========================================
@@ -22,6 +26,6 @@ SET(SRCS_CONSTRAINT ${SRCS_CONSTRAINT}
 # Forward var to parent scope
 # These lines always at the end
 SET(HDRS_CONSTRAINT ${HDRS_CONSTRAINT}  PARENT_SCOPE)
-SET(SRCS_CONSTRAINT ${SRCS_CONSTRAINT}   PARENT_SCOPE)
+SET(SRCS_CONSTRAINT ${SRCS_CONSTRAINT}  PARENT_SCOPE)
 
   
\ No newline at end of file