This PR revises the formulation of the legacy K-profile parameterization (KPP) ocean boundary layer scheme. It incorporates:

1.  a non-local momentum flux—the Flux-profile parameterization (`FPMIX`); when the local shear is not aligned with the wind, this scheme adds a non-local momentum flux in the direction of the wind; and 
2.  mixing with and without waves following the Monin-Obukhov Similarity Theory expanded to include Stokes drift (`STOKES_MOST`). This option provides the transition from waveless to ocean surface waves in any stage of growth or decay.

**Summary:**

* Uncomment omega w2x entries;
* Simplify the nonlocal increments in `vertFPMix`;
* In the call to `CVmix_kpp_compute_unresolved_shear`, passes the 2D surface buoyancy flux (`surfBuoyFlux2`) instead of the 1D version (`surfBuoyFlux`), which is preferable. **This is answer changing**;
* Remove `uold` and `vold` diagnostics. These were used in an alternative time-stepping scheme that is now obsolete; 
* Pass boundary layer depths to the RK2 and add consistency check to make sure `FPMix` is always used with `SPLIT`;
* Add the capability to mix down the Eulerian gradient instead of the Lagrangian;
* Make a minimum set of `FPMix` diagnostics available.

This PR relies on https://github.com/CVMix/CVMix-src/pull/94/. 

New diagnostics:
```

"StokesXI"  
    ! modules: {ocean_model,ocean_model_d2}
    ! long_name: Stokes Similarity Parameter
    ! units: nondim
    ! cell_methods: xh:mean yh:mean area:mean

"Lam2"  
    ! modules: {ocean_model,ocean_model_d2}
    ! long_name: Ustk0_ustar
    ! units: nondim
    ! cell_methods: xh:mean yh:mean area:mean

"uE_h" 
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: x-zonal Eulerian
    ! units: m s-1
    ! cell_methods: xh:mean yh:mean zl:mean area:mean
    ! variants: {uE_h,uE_h_xyave}

"vE_h" 
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: y-merid Eulerian
    ! units: m s-1
    ! cell_methods: xh:mean yh:mean zl:mean area:mean
    ! variants: {vE_h,vE_h_xyave}

"uInc_h"  
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: x-zonal Eulerian
    ! units: m s-1
    ! cell_methods: xh:mean yh:mean zl:mean area:mean
    ! variants: {uInc_h,uInc_h_xyave}

"vInc_h"  
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: x-zonal Eulerian
    ! units: m s-1
    ! cell_methods: xh:mean yh:mean zl:mean area:mean
    ! variants: {vInc_h,vInc_h_xyave}

"uStk" 
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: x-FP du increment
    ! units: m s-1
    ! cell_methods: xh:mean yh:mean zl:mean area:mean
    ! variants: {uStk,uStk_xyave}

"vStk"  
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: y-FP dv increment
    ! units: m s-1
    ! cell_methods: xh:mean yh:mean zl:mean area:mean
    ! variants: {vStk,vStk_xyave}

"Omega_tau2s" 
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: Stress direction from shear
    ! units: radians
    ! cell_methods: xh:mean yh:mean zi:point area:mean
    ! variants: {Omega_tau2s,Omega_tau2s_xyave}

"Omega_tau2w"  
    ! modules: {ocean_model,ocean_model_z,ocean_model_rho2,ocean_model_d2,ocean_model_z_d2,ocean_model_rho2_d2}
    ! long_name: Stress direction from wind
    ! units: radians
    ! cell_methods: xh:mean yh:mean zi:point area:mean
    ! variants: {Omega_tau2w,Omega_tau2w_xyave}

"uStk0"  
    ! modules: {ocean_model,ocean_model_d2}
    ! long_name: Zonal Surface Stokes
    ! units: m s-1
    ! cell_methods: xh:mean yh:mean area:mean

"vStk0"  
    ! modules: {ocean_model,ocean_model_d2}
    ! long_name: Merid Surface Stokes
    ! units: m s-1
    ! cell_methods: xh:mean yh:mean area:mean
```