[SB/MRH][76549318] trigger new event when clearing errors

Initial use case is for AG feature flip story for handling
register/login errors differently in the UI.
https://www.pivotaltracker.com/story/show/76549318
[SB/MRH][76549318] change event name
[SB/MRH][76549318] allow disabling of email prefill

We want to disable this behavior in an AG feature flip.
Merge pull request #3 from primedia/sb_mrh_76549318_add_trigger_when_clearing_errors

[SB/MRH][76549318] trigger new event when clearing errors