Added `openssl_verify_mode` parameter for action_mailer.

- parameter in `environments/production.rb`
- documentation & default value (nil) in `discourse_defaults.conf`
FIX: Allow users to create protocol relative URLs in posts.
Add a way to show a custom message at the top of all notification emails. Customize it at /admin/site_contents/notification_email_top
update logster
remove subcategories text from categories page
minor copy improvement
minor mobile fixes
FEATURE: logster logs js errors
fix mobile badge colors, jay leno P chins
bit more mobile css cleanup
Wiki Post
Merge pull request #2303 from velesin/wiki_topic

wiki topic
Fix my prev_page code, thanks to riking
BUGFIX: better resiliency in the backup/restore processes
BUGFIX: add 'notify_moderators' flag reason
Don't show suspended users in autocomplete fields unless you are staff
BUGFIX: missing <tbody> tag inside a <table>
BUGFIX: moderators can notify moderators
BUGFIX: center title columns in basic topic lists
Add an ENV variable to enable the stricter, plugin-incompatible ES6
behaviour for development.