Update-courselist's base-path refernces config

refs #63

To test the changes switch to this branch and copy the new line from
config/default.py.dist to config/default.py (config/default.py isn't
tracked so this change has to be made manually)

Renamed UPDATE_COURSE_BASE_PATH to MOODLE_*

Changed variable name to MOODLE_COURSE_BASE_PATH
refs #75 comment for orvsd_central/controllers/category.py:174

Updated comments