seems like we need to define COURSES_WITH_UNSAFE_CODE in cms.envs.common.py, although cms.envs.common.py imports lms.envs.common (where this is defined).
also add some defaulting to the querying of the settings where it defaults to an empty set
add simple unit test on the defaulting of the settings
Merge pull request #372 from edx/fix/cdodge/update-localdev-setting-for-unsafe-courses

Fix/cdodge/update localdev setting for unsafe courses