add profile option for edit history, visible only when edit history is disabled globally.
discourse#2591
add spec for public edit history
Add Access-Control-Allow-Credentials to the CORS headers.
Merge pull request #2604 from vikhyat/fix-cors

Add Access-Control-Allow-Credentials
Merge pull request #2591 from BenLubar/benlubar-edit-history-public

add profile option for edit history visibility