fixes for verification ui discrepancies
UX-351
i18n for self-assessment (ORA-314)

make openendedchild and open_ended_module_v1 act enough like xblocks to get xblock 18n
Enable download_track for existing courses if self.track.
Merge pull request #2620 from edx/alex/fix_enable_download_track

Enable download_track for existing courses if self.track.
Merge pull request #2575 from edx/adam/i18n-self-assessment-2

Adam/i18n self assessment 2
Merge pull request #2563 from edx/frances/fix/verified-ui-fixes

Fixes for verification UI discrepancies