(this was partially inspired by discussion in #726)

Right now, to create a new Column in a table, you have to do:

tab.add_column(Column(...))

that is, you have to explicitly create a Column object, even if that's the only thing you pass into add_column. I propose to enhance this to allow the following usage:

tab.add_column(name='a',data=somearray)

which would be the same as

tab.add_column(Column(name='a',data=somearray))

This would be fully backwards-compatible. The only catch is that the index and col keywords have to be available to add_column, so they can't be passed on to Column. This doesn't seem too much of a problem, though, because Column doesn't currently have either keyword (and I can't think of any reason why it would in the future).

I'm happy to implement this myself, but if @taldcroft or @astrofrog think it's a bad idea, I don't want to spend the time to do so.