Support "A3:A" style references?

[cmcaine]

In Excel, this refers to all the cells in the A column from row 3 till the bottom.

It would have been convenient for my use case to have this select from row 3 till the last row with any non-missing cells.

[davidanthoff]

Yes, good idea! I won't have time to implement this anytime soon, but a PR that does would be great.