Add some caching of the equation system (LocusEquation) to avoid heavy computations

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34030 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#3392 Help button for Interval tab on the web.

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34031 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e