CRUD now working! Sequelize models refactored. Sequelize migrations added.

[YSHebron]

Some reminders ^^

1. Yung ./backend ay ./api na ngayon
2. Yung ./backend/server.js ay ./api/app.js na ngayon
3. Wala pang matinong Joi validation dun sa ./api/controllers/jeepsController.
4. Baka pwede pa ibreak-up yung ./api/controllers/jeepsController into separate files (but it's working na).
5. Medyo isolated yung jeeps routes from user routes (yung sa authentication), but they're both working now.
6. Use Sequelize CLI for migrations.
7. No Sequelize seeders atm.

TODOs:

• [x] Add updated frontend files, with CRUD UI.
• [x] Connect CRUD UI with CRUD API.
• [ ] Add Route class (with array routes).
• [ ] Add Driver class (with array drivers).
• [ ] Add Route layers to map. Colored. Note that color is an attribute of route table. Please use it by fetching from /api/jeeps/route.
• [ ] Change marker colors depending on route color.
• [ ] Check out each endpoint for idea on what to do, also check out database schema (sesend ko).
• [x] To me: Send sample POSTs, PUTs, and DELETEs.