Requirements editor syntax checking

[venkatesh-sivaraman]

After the most recent catalog update, a syntax error in the course 6 minor requirements list caused the Android app to crash on launch. Postmortem: the edit request system needs a syntax checker that prevents the deployment of incorrectly-formatted requirements. This can be either on the end-user side (preventing them from submitting edit requests that have errors) or more likely on the reviewer side (preventing them from deploying).