ArePerpendicular, IsIsoscelesTriangle rewrite; equalityString simplification (new Relation Tool)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34730 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#4368 preview in dialog

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34731 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e