Load Neural Net

[jatkinson1000]

Closes #11

This is built on top of #9 which is itself build upon #4 and #5.

Testing using the CAM_GW_Net case on Derecho.

• [x] Add filepath to neural net that can be read in from the namelist
• [x] Read in and scatter to processes
• [x] Generate a net on each process in the setup
• [x] Destroy at the end of the physics routine

[jatkinson1000]

This is now ready for review.

It loads the net during the init phase of the simulation, and adds a gw_final subroutine to destroy it at the end. The net is then available to be called within the gw_drag module as a module variable.