Refactor courses to be enrolled and planned courses. Added course tabs.

src/app/core/models/course.ts

src/app/core/models/planned-term.ts

...egree-planner/shared/course-item/course-item.component.ts

src/app/degree-planner/store/effects/plan.effects.ts

src/app/degree-planner/store/reducer.ts

...gree-planner/term-container/term-container.component.html

...gree-planner/term-container/term-container.component.scss

...degree-planner/term-container/term-container.component.ts