Merge branch 'rtong' into bowen
commit
Merge branch 'bowen' into rtong
update session timeout handling
update database
Merge branch 'bowen' into rtong
Merge branch 'bowen' into Bohan-Zheng
add comment for action.js
fix bug with real data

fix lalala
fix null pointer
hello bowen
Merge branch 'rtong' into bowen
update button
add comment for semester.js
expand and undo
change
first page undo complete

by now, no bugs found
add auto_assign_button

add 5 functions:
1. expand()
2. expandAll()
3. shrink()
4. shrinkAll()
5. undo_assign()
Merge branch 'master' into rtong
Merge branch 'bowen' into rtong
select madantory courses