Update Admin constructor and Student add appointment method name

src/main/java/softeng/g4/Main.java

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

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

src/main/java/softeng/g4/courselist.txt

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

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

src/main/java/softeng/g4/userlist.txt

src/test/java/softeng/g4/user/TeachingAssistantTest.java