Merged in NRAO changes until 12-Nov-2013


git-svn-id: http://casacore.googlecode.com/svn/branches/nrao-nov12@21401 6afa274c-0927-0410-9b47-a1284d797885
Merged in NRAO changes till 28-Nov-2013


git-svn-id: http://casacore.googlecode.com/svn/branches/nrao-nov12@21402 6afa274c-0927-0410-9b47-a1284d797885
Added GROUPBY and aggregate functions to TaQL


git-svn-id: http://casacore.googlecode.com/svn/branches/nrao-nov12@21403 6afa274c-0927-0410-9b47-a1284d797885
Added test program tExprGroup and fixed a few small aggregate errors


git-svn-id: http://casacore.googlecode.com/svn/branches/nrao-nov12@21404 6afa274c-0927-0410-9b47-a1284d797885
Execute possible HAVING clause
Optimize for single GROUPBY keys


git-svn-id: http://casacore.googlecode.com/svn/branches/nrao-nov12@21405 6afa274c-0927-0410-9b47-a1284d797885