ENH: add explicit doubleVector, doubleTensor typedefs

- the counterpart to floatVector, doubleTensor, which can be useful
  for connecting to programs that always expect double precision for
  the arguments, when using single-precision for OpenFOAM itself.

  Eg,
     doubleVector pos = ...;
     vtkcamera->SetPosition(pos.v_);

src/OpenFOAM/primitives/Vector/floatVector/floatVector.C

@@ -21,9 +21,6 @@ License
     You should have received a copy of the GNU General Public License
     along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
-Description
-    Vector of floats.
-
 \*---------------------------------------------------------------------------*/
 
 #include "floatVector.H"