Statistics subfigure enhancement/bugfix

For Collaborative Statistics text, independent images are labeled (a), (b), as in Figure 1.2a, Figure 1.2b.  Unlike previous texts, it was requested that the subfigure alpha character be a part of the target-link.  XSL code was created by Phil to address this enhancement.  Numbering.less was updated as well to utilize the subfigure counter and the link target subfigure