Merge stable into default (NON-TRIVIAL)
- dropping __future__ statement added by d2472948da9c
- added migration from 407acc41beb5 to migration file for 3.16.1
option_group_changed('port', 'main', 'web')
option_group_changed('query-log-file', 'main', 'web')
option_group_changed('profile', 'main', 'web')
option_group_changed('max-post-length', 'main', 'web')