Matlab package

The functions are now under the "gemscr" package so we don't have to add lots of folders to PATH--just the top-level folder.

put code under matlab/

all matlab code is under matlab/ directory. This allows addpath() to avoid grabbing old/conflicting code, which was happening before this change.

Run setup in the Matlab console to setup the paths.

KHI JGR paper

Andres et al, 2020