make sure 1.2 not displayed as 1.2000000000001 when rounding set to 15sf

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@29389 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#3691 TrimmedIntersectionLinesModel and applied to web.

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@29391 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e