lesson <div> - separate lesson type and lesson group

For instance, a lesson type "Lecture" of group "V2" will be split into
the lesson type text "Lecture", followed by a span of class
`lesson-group` with text "V2". This is to enable the toggling of
visibility of the lesson group in an upcoming patch.

Signed-off-by: Pang Yan Han <pangyanhan@gmail.com>
lesson <div> - Add CSS class `venue` for venue paragraph

For toggling of visibility using the Show / Hide controls in an upcoming
patch.

Signed-off-by: Pang Yan Han <pangyanhan@gmail.com>
lesson <div> - add paragraph containing frequency of lessons

for lessons which do not occur weekly

Signed-off-by: Pang Yan Han <pangyanhan@gmail.com>
Enable Show / Hide controls

The Show / Hide controls sit above the Select2 box on the `Timetable
Builder` page, and enables us to toggle the visibility of the following
information of lesson <div>s:

- Module Code
- Lesson Group
- Venue
- Module Name
- Weeks the lesson occurs

Clever use of CSS classes on the #timetable <table> to toggle visibility
of information in its descendent lesson <div>s, along with jQuery code
to toggle the addition/removal of those classes are the key parts of
this patch.

Signed-off-by: Pang Yan Han <pangyanhan@gmail.com>