[DS-1008] Encapsulate AT DB Connection and clean up

    - Factor out Mongo connection into its own class
    - Refactored ugly multiple if statements into hash
    - Remove unneeded JSON parsing
[DS-1008] Simplify Odin data generation acceptance tests
[DS-1008] Improve Section CRUD AT
[DS-1008] Reinstate feature required for use by other ATs
[DS-1008] Fix count of bell schedules in AT
[DS-1008] Fix odin tests by generating 10students_optional scenario
Merge branch 'master' into ds-917