Make sure ExpressionNode does not depend on App

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25881 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Use space to make sure invalid input a\b throws error

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25882 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
typo (missing space)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25883 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Spline: export Asymptote, Pstricks, Pgf

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25884 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
More static stuff in EN serialization

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25885 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e