Check for worker URLs

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36389 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#4545 - rename in CAS succeeds

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36390 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Check for worker URLs

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36391 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Save files locally if user decides not log in to GGBTube (web)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36392 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e