Advanced admin page

[jvmespark]

Issue closes: #824

Database Changes/Migrations TODO If you added/modified a table, notify people of schema change here Example:

Added table account_semester_selection for a mapping from a students account and semester to a class and section (aka class/section selections)

Test Modifications TODO Note added unit/integration tests: (all backend changes should contain unit/integration tests with pytest) Example:

Added test tests/api/db/test_classinfo.py:test_crn_uniqueness to ensure all classes returned from API call don't have repeat CRNs

Photos TODO Show before and after, capture screenshot/gif of finished feature/bug