Update redirect and wording for prof ed

- Changes registraiton button text for professional ed courses
- Professional ed courses do not see "choose your track" page; go straight to verification flow
Adapt flow for new 'professional' mode.

ECOM-41
Add integration tests for professional ed flow
LMS: adding rendering/styling support for initial professional ed course types on student dashboard
Consider profession ed courses as paid courses.

ECOM-63
Merge pull request #4801 from edx/prof-ed-cherry-picked-changes

hotfix-2014-08-12
Check REQUEST_CONTEXT.context exists before accessing it.

LMS-11226