Fixed use of showcol=True in showStructure


git-svn-id: http://casacore.googlecode.com/svn/trunk@21391 6afa274c-0927-0410-9b47-a1284d797885
Extend try/catch block


git-svn-id: http://casacore.googlecode.com/svn/trunk@21392 6afa274c-0927-0410-9b47-a1284d797885
Removed setting of userblock which reserved needlessly 32K file space.


git-svn-id: http://casacore.googlecode.com/svn/trunk@21393 6afa274c-0927-0410-9b47-a1284d797885