====== fieldprops ======

print out basic properties of a FlowField

<code>
options :
  -g        --geometry                                             show geometrical properties
  -m        --mean                                                 show mean properties
  -n        --norm                                                 show norm properties
  -sp       --spectral                                             show spectral properties
  -sy       --symmetry                                             show symmetry properties
  -d        --dynamic                                              show dynamical properties
  -e        --energy                                               show energy properties
  -R        --Reynolds          <real>      default == 400         Reynolds number
  -eps      --eps               <real>      default == 1e-07       spectral noise floor
  -dt       --dt                <real>      default == 0.03125     integration time for du/dt estimate
  -T        --T                 <real>      default == 0.03125     integration time for du/dt estimate
  -nl       --nonlinearity      <string>    default == rot         method for  u grad u [rot or skw]
  -dg       --digits            <int>       default == 6           digits of output for reals
  <flowfield>      (trailing arg 1)                                input field
</code>

Definitions: The norms and energy measures reported by the -n and -e options are defined as follows

<latex> $ \begin{align*}
 \text{L2Norm} \quad   \|u\|  &= \left(\frac{1}{L_x L_y L_z} \int_{\Omega} \|{\bf u}\|^2\,\, d{\bf x} \right)^{1/2}\\
 \text{energy} \quad   E(u) &= \frac{1}{2 L_x L_y L_z} \int_{\Omega} \|{\bf u}\|^2\,\, d{\bf x}  \\
 \text{dissipation}  \quad  D(u) &= \frac{1}{L_x L_y L_z} \int_{\Omega} \|\nabla \times {\bf u}\|^2 \,\, d{\bf x} \\
 \text{forcing}  \quad  I(u) &= \frac{1}{L_x L_z} \int_{y=a,b} \frac{\partial u}{\partial y} \, dx dz
\end{align*} $ </latex>

FIXME: Some of the measures output by fieldprops assume that the field is the fluctuating velocity field 
of plane Couette flow, and some quantities are reported for the total velocity field %%u+U%% where %U(y) = y%%.
There should be an option for specifying other common base-flow / fluctuation decompositions, or none.