Make the met script compatible with APCEMM 1.2

[Calebsakhtar]

I noticed that as of version 1.2 the met files produced by the scripts are no longer compatible with APCEMM.

This PR addresses that by:

• Adding a way to specify the vertical velocity "w".
• Adding a default entry (populated by ones) for the stretch.
• Adding a reference time.
• Removing the water relative humidity.

[Calebsakhtar]

@sdeastham Would you mind reviewing this?

[Calebsakhtar]

@sdeastham Just bumping this

[sdeastham]

Thanks @Calebsakhtar ! One change request - can you update the units of w in the script to be in Pa s-1, not m/s? The routine now uses pressure-velocity (it's both more convenient for the code and more common as an output from GCMs)

[Calebsakhtar]

Hi @sdeastham, I finally got round to doing this. Sorry for combining the commit with the application of Black Formatter. Hopefully it looks better though!