Doc: Moved FLUX_ISO and CLASS_STAR to isophotal measurement section (which is still named Position.rst, for portability reasons).
Doc: Added ISOAREA description in isophotal shape section.

Doc: added a first batch of model-fitting parameters to the list of measurements.

Doc: Customized CSS to have equation permalinks visible when hovering the mouse.

Doc: removed non-compliant characters in citation labels that would create problems with Sphinx v1.6+ (see https://github.com/sphinx-doc/sphinx/issues/3917).