Put ErrorHandler back to Dialogs

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37851 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Ticket #3420: Internet Explorer still resists, custom confirm dialog does not work either (so it shall window.prompt only if security settings allow it)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37852 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Ticket #3420: unused method should be commented out

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37853 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#4785 fixed

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37854 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Fixing first part of #4786

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37855 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
User can remove the image of turtle - on desktop. (#4721)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37856 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e