Added table.__getattr__ to use a column as attribute(e.g. t.DATA[0])

git-svn-id: http://pyrap.googlecode.com/svn/trunk@346 80e5cd9e-5d28-0410-a7fc-3f808f404835
Documented new way to use a column name as attribute


git-svn-id: http://pyrap.googlecode.com/svn/trunk@347 80e5cd9e-5d28-0410-a7fc-3f808f404835
Improved checking of (slice) indices

git-svn-id: http://pyrap.googlecode.com/svn/trunk@348 80e5cd9e-5d28-0410-a7fc-3f808f404835
Added handling of keywords in getattr and getitem

git-svn-id: http://pyrap.googlecode.com/svn/trunk@349 80e5cd9e-5d28-0410-a7fc-3f808f404835
_ or keys means all keywords

git-svn-id: http://pyrap.googlecode.com/svn/trunk@350 80e5cd9e-5d28-0410-a7fc-3f808f404835