[courseware] generate sequence-specific titles server-side (AC-695)

[courseware] generate sequence-specific titles server-side (AC-695)

case for empty subsections [AC-695]

move title logic into courseware context method [AC-695]

pep8

coffeescript -> js

js mistake

jslint

refactor sequence title generation slightly

missed a line

line too long

python is not javascript

ugh js

ugh js part 2