Test case added for substituting with keep input #4739 (related #3557)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37863 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Ticket #4660: the original part of this ticket was easy (insertFile in App3D case)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37864 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e