Deleting a variable - Change let to unlet

Created by: jhod0

Current syntax for deleting a variable:

# let date=2016
# echo $date
2016
# let date
# echo $date

In my opinion, this is very ambiguous syntax. I think unlet would make a lot more sense for deleting a variable, like so:

# let date=2016
# unlet date

This seems like a much more natural choice.