make arrow-heads a bit bigger for line thickness 8-13

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25054 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
AlgebraView can be toggled, EuclidianView resizes automatically

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25055 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
fix mistake in ExpressionNode.negation() in r25019

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25056 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e