#116 Update to MathMod-12.1

[Abderrahman Taha]

MathMod Version 12.1 Release Notes

1) Added "SeaShells_Mathematical_Modeling" script to model "Lyria","Wentletrap","Conus","Natalina"and "Ammonite" SeaShells.
2) Bug-fixes, code optimization and documentation update.
3) For a complete list of changes made during the course of development, please visit: MathMod-12.1 (github.com)