Refactor main and test directory, and Add test for TeachingAssistant.java

out/production/tasc/softeng/g4/Main.class

out/production/tasc/softeng/g4/calendar/Calendar.class

out/production/tasc/softeng/g4/courselist.txt

out/production/tasc/softeng/g4/user/TeachingAssistant.class

out/test/tasc/softeng/g4/user/StudentTest.class

out/test/tasc/softeng/g4/user/TeachingAssistantTest.class

src/main/softeng/g4/Main.java

src/main/softeng/g4/appointment/Appointment.java

src/main/softeng/g4/appointment/Reminder.java

src/main/softeng/g4/appointment/RequestAppointment.java

src/main/softeng/g4/calendar/Calendar.java

src/main/softeng/g4/calendar/Schedule.java

src/main/softeng/g4/cli/TACLI.java

src/main/softeng/g4/course/Course.java

src/main/softeng/g4/course/CourseList.java

src/main/softeng/g4/courselist.txt

src/main/softeng/g4/user/Admin.java

src/main/softeng/g4/user/Student.java

src/main/softeng/g4/user/TeachingAssistant.java

src/main/softeng/g4/user/User.java