Ticket #3874: this commit is not a feature, just some efficiency coming into my mind

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34988 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Ticket #4388: I think that CAS cell geos should be allowed as well, but this doesn't help in the actual problem (also, note that InsertFile is not like Open File, so it won't insert geos depending on axis, for example, which might be enhanced later).

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34989 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e