Put notes to section slides to a dummy slide

[Issue #3]

Notes to section slides were put in a separate slide, which is not very
optimized, causing display problems and inconsistency. Now all notes are
3rd level titles, css styling becomes easier.
Notes not in new page in prints

[Issue #4]

page-break changed from always to avoid.
Comment out trivial notes
Remove redundant notes

[Issue #3]

The notes causes styling and slide level recognition problems.
Set narrow lines for all li in print view

[Issue #4]