Mars Subsurface Ice Model (MSIM) Program Collection

Reorganization of the directories and minor edits over the past year.

Mars Subsurface Ice Model

First release of the Mars Subsurface Ice Model (MSIM) in a dedicated repository. Most of MSIM is almost 20 years old. Over the past 7 years, it was distributed as part of the "Planetary Code Collection". MSIM finally has its own repository. This first release starts with version number 1.2.0, because the latest version of the Planetary Code Collection was 1.1.9.