Phase 1 of UW PBL CCPPization, cleanup to vertical_diffusion_tend

[jimmielin]

Companion PR ESCOMP/atmospheric_physics#337

Purpose of changes (include the issue number and title text for each relevant GitHub issue):

• Move University of Washington moist turbulence scheme ("diag_TKE", CAM5 PBL scheme) to atmos_phys.
• Cleanup to vertical_diffusion_tend to accommodate CCPPization of HB (CAM4) and UW (CAM5) PBL schemes.
• Minor fixes to snapshot metadata.

Describe any changes made to build system: added bretherton_park folder to atmos_phys

Describe any changes made to the namelist: update to descriptions only.

List any changes to the defaults for the boundary datasets: N/A

Describe any substantial timing or memory changes: None

Code reviewed by:

List all files eliminated:

D       src/physics/cam/eddy_diff.F90
  - moved to atmos_phys

D       src/physics/cam/pbl_utils.F90
  - only remaining subroutine now in atmos_phys bretherton_park_diff.F90

List all files added and what they do:

List all existing files that have been modified, and describe the changes:

M       bld/configure
  - add bretherton_park subdir for atmos_phys

M       bld/namelist_files/namelist_definition.xml
  - fix description

M       src/control/cam_snapshot_common.F90
  - populate units for pbuf_ksrftms, pbuf_WSEDL

M       src/physics/cam/eddy_diff_cam.F90
  - moved most of existing logic in eddy_diff_tend to new CCPP scheme bretherton_park_diff_run
  - what remains is just CAM-specific code for history and code to interface with the underlying run phase.

M       src/physics/cam/vertical_diffusion.F90
  - move kinematic fluxes and obklen calculation to common interstitial scheme.
  - move input preparation (vert coord for vdiff, potential temp) to common interstitial scheme.
  - rearrange data flow for HB, UW to share as much code as possible.