[Feature 3] User creates a Task

[XinyingXu]

User wants to create a task. They can choose from a couple of default assignment types to create a CustomTask (which has default study techniques), or leave it blank to create a Task. They enter Name, Course, Priority (enum) , Deadline and links to notes for the task, and a StudyDeadline that is (potentially) 3 days before the Deadline is created for the task. The task then gets added to the TODOlist, which is sorted based on deadlines.

Entity: Task, CustomTask