Add penetrative shortwave coupling

[kieranricardo]

Add penetrative shortwave radiation coupling from the UM to CICE. Involves:

1. Turning on shortwave calculations in the UM.
2. Add shortwave coupling fields to the UM and CICE caps.
3. Changing CICE and icepack to accept and penetrating shortwave.
4. Testing changes.

Normally CICE and icepack calculate penetrating shortwave from downward surface shortwave, but the UM includes this in its boundary layer scheme so we will have to make changes to CICE and icepack to accept and use provided penetrating shortwave. Will likely require changes to the CICE/icepack vertical thermodynamics and energy budget, and may need to make use of some (or none) of the existing CICE/icepack penetrating shortwave calculations.