Added parallelized mergesort


git-svn-id: http://casacore.googlecode.com/svn/branches/nrao-nov12@21299 6afa274c-0927-0410-9b47-a1284d797885
Fixed little error in size of sort block


git-svn-id: http://casacore.googlecode.com/svn/branches/nrao-nov12@21300 6afa274c-0927-0410-9b47-a1284d797885
Replace ROTableColumn by TableColumn


git-svn-id: http://casacore.googlecode.com/svn/branches/nrao-nov12@21301 6afa274c-0927-0410-9b47-a1284d797885