Updated DEMO files.

Several cleanups and such. You will need to pull the DEMO files from my [mineos-demo repo](https://github.com/QuLogic/mineos-demo) because I don't have push access on the geodynamics repo.

* Ignore DEMO3 results in git.
* Make scripts work without modifying PATH or installing.
* Reformat and fix typos in README files.
* Remove invalid models from script.
* Remove duplicate DEMO files.
* Exit with correct status when scripts fail.
* Make POSIX sh scripts usable.
* Fix several typos in scripts.
* Remove csh shell scripts.