Automate Tube Capping

[jshmu]

Users often want to keep a tube closed when they aren't explicitly using it within a protocol (to prevent evaporation, avoid any chance of contamination, etc). Currently, we just add a pause or delay in the protocol to give the user time to cap/uncap their tubes. We should totally automate this!

Make an add-on device for the OT-2 that can remove the cap from a tube and/or put the cap back on. You can design the device for any one of more tube type. This can be a rough off-robot prototype or integrated with the Opentrons API. All stages of "functional" are acceptable!