Add Gates for Authorization

[hanisirfan]

Gates

• authUser - Check whether current authenticated user allowed to access the page. Ex: User Profile.
• authLecturer - Check if lecturer could access anything allowed for them.
• authCoordinator - Check if lecturer is a classroom coordinator of a student.
• authAdmin - Check whether current authenticated user is admin.
• authSuperAdmin - Check whether current authenticated user is super admin.

Middleware

• auth - Default Laravel auth middleware. Check if user is authenticated. If not redirect to / aka login page.
• userIsAdmin - Check if current authenticated user is an Admin. If not, abort with 403.
• userIsSuperAdmin - Check if current authenticated user is an SuperAdmin. If not, abort with 403.

[hanisirfan]

Added to #5.