FEATURE: Add Archive Topics to Bulk actions

Add the ability to archive topics in bulk
https://meta.discourse.org/t/archive-topics-via-bulk/20302
Merge pull request #2814 from cpradio/add-bulk-archive-option

FEATURE: Add Archive Topics to Bulk actions
add a plugin outlet under avatars beside posts
FIX: j/k place tab focus accordingly so tab will go to the first linked item in the selected post/row

Allow tabbing to continue from the selected post/topic when using the j/k keyboard shortcuts
https://meta.discourse.org/t/when-a-post-is-selected-tab-should-take-you-to-the-first-link/16212
improve HTML plain text email error copy
FIX: Allow proper escaping of bold and italics markdown, even when
nested.
Merge pull request #2815 from cpradio/tab-to-first-link-on-post-when-using-keyboard

FIX: j/k place tab focus accordingly so tab will go to the first linked ...
FIX: allow API to create users when invite_only is true
FIX: send content length with backups
improve debuggability of code
fix test
correct mobile login form layout error
tighten spacing on mobile dialog headers
few more mobile login style fixes
bigger mobile topic list post count and date tap targets
mobile login form tweaks
more mobile login form tweaks
FEATURE: api support for arbitrary unlinked assets

admins can set retain periods for assets
FEATURE: allow a central redis cache for assets
mobile need space between dismiss posts/topic btn