Add baseview(extended from backbone view), which can further extended by other views + Add fucntion to modify iframe and embed tags + add related tests
STUD-823

Make sure that changing grading cutoffs triggers a save confirmation, and reliable reverting of changes.

Rather than asynchronously saving when a setting is updated, we now
prompt the user to confirm their changes and only persist the data if
they hit the save button. Lettuce tests are updated to expect this
behavior and some new ones are added.

When all settings require an explicit save, this functionality will be
shared between each view (with slight changes, e.g. click handlers.)

And delete `CMS.ServerError`

https://edx.lighthouseapp.com/projects/102637/tickets/232

errors when there are parent and child views both defining on error
handlers still.