====== L2IP ======

compute the L2 inner product between two fields

options
<code>
  -d        --digits             <int>   default == 7   number of digits
  -n        --normalize                                 normalize by norms of each field
  <flowfield>  (trailing arg 2)                         input field #1
  <flowfield>  (trailing arg 1)                         input field #2
</code>

usage
<code>
L2IP u.ff v.ff
</code>

returns 

<latex>
 \text{L2IP(u,v)} = ({\bf u}, {\bf v})  = \frac{1}{L_x L_y L_z} \int_{\Omega} {\bf u} \cdot {\bf v} \,\, d{\bf x}
</latex>

or, if -n option is specified, %%L2IP(u,v) / (L2Norm(u) L2Norm(v))%%