Usage: <tt>input = <i>s</i>  interpCN</tt>

<p>
Make the current configuration <tt>SR</tt> a linear interpolation between
<tt>SR1</tt> and <tt>SR2</tt>.  <tt>SR[i] = (1-<i>s</i>)*SR1[i] + s*SR2[i]</tt>.
The center of mass difference between <tt>SR1</tt> and <tt>SR2</tt> is removed
from <tt>SR</tt>.

<p>
Also see <tt>setconfig1</tt>, <tt>setconfig2</tt>, <tt>constrainedrelax</tt>.

