* Add recovery code support for two-factor auth
When users enable two-factor auth, the app now generates ten
single-use recovery codes. Users are encouraged to print the codes
and store them in a safe place.
The two-factor prompt during login now accepts both OTP codes and
recovery codes.
The two-factor settings UI allows users to regenerated lost
recovery codes. Users who have set up two-factor auth prior to
this feature being added can use it to generate recovery codes
for the first time.
Fixes#563 and fixes#987
* Set OTP_SECRET in test enviroment
* add missing .html to view file names
