Fixed installation of header files.

src/TNL/Communicators/CMakeLists.txt

 SET( headers MpiCommunicator.h
              NoDistrCommunicator.h )
 
-INSTALL( FILES ${headers} DESTINATION include/tnl-${tnlVersion}/TNL/Communicators )
+INSTALL( FILES ${headers} DESTINATION ${TNL_TARGET_INCLUDE_DIRECTORY}/Communicators )

src/TNL/Meshes/DistributedMeshes/CMakeLists.txt

-SET( headers DistributedMesh.h
+SET( headers BufferEntitiesHelper.h
+             DistributedMesh.h
              DistributedMeshSynchronizer.h
              DistributedGrid_1D.h
              DistributedGrid_2D.h