job opening and job type updates

notes:
- make sure to use the new database schema and data file:
AES_SQL_Query_Iter2-v1.sql

iter2-v1 changes:
- added "Approved" column to JobOpening table (for HiringManager to
request jobs and have StoreManager approve)
- added HiringManager and StoreManager roles and users

general additions:
- added index view for all job types (/Jobs/Index)
- added index view for all job openings (/JobOpenings/Index)
- added ability to create job types (for HiringManager role)
- added ability to create job opening (for HiringManager role)
- added ability to approve job opening (for StoreManager role)
- added ability to reject job opening (for StoreManager role)