Compilation of the model

[rs028]

• the mistra executable should maybe sit in the main directory rather than in src/, or in a separate bin/ directory.
• are 2 Makefiles (and hence two compilation steps) really needed? There is one Makefile in the src/ directory and one in the src/mech/ directory.
• does it make more sense for the mech/ directory to be moved out of src/ and into the main directory?

[rs028]

Related to this point: the Makefiles may need to be modified by the user. Add them to .gitignore?