General-Parameters.md

 See #11 and #12 ans well as the current grammar.
 
 - General parameter settings
+  - model size
+  - distribution of model tiles on multiple CPUs/processes/threads
 - General feature settings
 
 See also https://mitgcm.readthedocs.io/en/latest/getting_started/getting_started.html#parameters-configuration-computational-domain-geometry-and-time-discretization