Keep MPAS SCRATCH files open during init, run and finalization

Previously, SCRATCH files were opened and closed in each init, run and
finalization step. With large number of MPI ranks that may
overwhelm a file system. This will instead open per-process SCRATCH
files once in init step and close once in final step, keeping them
open in each run step.

share/csm_share/README

@@ -0,0 +1,31 @@
+!===============================================================================
+! SVN $Id: README 19883 2009-12-14 23:19:10Z erik $
+! SVN $URL: https://svn-ccsm-models.cgd.ucar.edu/csm_share/trunk_tags/share3_150116/README $
+!===============================================================================
+
+                  A description of csm_share
+
+This module exists to collect code shared between various CCSM components.
+Excluding this "shared code" module, CCSM components are built using disjoint
+sets of source code.  The use of this shared code is similar to the use of
+object code libraries where each subdirectory of csm_share is equivalant to 
+one library.  While object library routines are accessed by linking to libraries 
+during the load phase, these shared code routines are accessed by including the 
+appropriate source code directory path during the compile phase.
+
+Motivation for this code sharing includes:
+
+- facilitating consistent physics between all models.  For example, uniform 
+  solar-zenith-angle/orbital calculations and uniform physical constants.
+- providing an interface/API between component models and the flux-coupler
+  component in the CCSM framework.
+- avoiding the need for redundant implementations of commonly needed 
+  functionality.  For example netCDF file reading, basic mapping (re-gridding)
+  functionality, and common character string manipulations.
+
+Current subsets ("libraries") of shared code only include:
+
+shr - very generic, general-purpose code that is likely to be useful to all 
+      CCSM components.  CCSM components may be explicitly required to use some 
+      parts of this code, for example the physical constants module.
+