Fixup makefiles so that these examples compile either as single directories or...

Fixup makefiles so that these examples compile either as single directories or as part of a build. Do not require special versions of GeoModel: I will propose that these examples be distributed not as useful compiled executables, but rather as source code, for people to learn from. Additionally, I believe that these should be carefully scrutinized and annotated with abundant comments for pedagogical purposes, and probably also referenced in the documentation.