Add coffeebot interactions to list/remove pending coffee orders

[katharosada]

Example:

If you want to cancel a coffee

       me: @coffeebot pending coffees
coffeebot: Fred will fetch you a Large Latte from Campos at 8:00am to be delivered to SIT Labs
       me: @coffeebot cancel my order
coffeebot: I've cancelled your order for a Large Latte

Of if they had a coffee in a run but the run has already closed (like within 20min):

       me: @coffeebot pending coffees
coffeebot: You have no coffees pending. There's a coffee for you in a recently-closed run, to be delivered to <place>

Of if the run has already closed:

       me: @coffeebot pending coffees
coffeebot: You have no coffees pending.

If the user has more than one coffee in the run, you have to specify the ID.