Restructure Repository

[jatkinson1000]

This should close #71 and #67

• separate CAM code from the core YOG parameterisation - see Move CAM interface code and tests out of NN_module  #67
• Avoid duplication of code or dual-maintained copies of files across the repository
  • Use references between directories
  • Move to CMake instead of Make to handle dependencies
• Move tests to their own location
  • Provide the option for users to specify what tests are built

[jatkinson1000]

Note that I have also removed the SAM interface file that was under development (see 2b3adf3).

This is because it is now deprecated and is no longer being pursued.
If returning it can be recovered from git history.

[jatkinson1000]

One question I have is should we perhaps rename "NN_module" to "YOG_convection"?

This would be much clearer.
If I recall NN_Module was only ever a placeholder until someone told Jim and I what the "neural net we extracted to a module" shoudl be called.

[MarionBWeinzierl]

We went through this together this morning and this makes sense. I have some very minor comments below, but otherwise it can be merged.

Regarding the question about the renaming, I agree that "YOG_convection" is a more meaningful name -- this change could be included in this PR

[jatkinson1000]

Hi @MarionBWeinzierl Made those changes as suggested.
I'll go ahead and merge shortly.