Allows us to easily define routes in plugins
Move `register_asset` into `PluginRegistry` -- the logic works better
there.
When using automatic file includes (es6, hbs) from plugins, allow the
asset pipeline to find new and deleted files with deleting the `tmp`
folder and restarting the server.
add embedding notes to admin quick start
add embedding notes to install doc
Update INSTALL-digital-ocean.md
show ungrouped emojis in tab, remove a few aliases

(I dislike :shit: and :squirrel: made no sense)

TODO: stop using symlinks for aliases
PERF: optimise rendering of posts
do we need #list-area margin-bottom so big?
FIX: properly unescape HTML entities in excerpts
FIX: Text in select2 dropdowns should not be variable since the
background is always white.
UX: Banner topics should be readable even with dark color schemes.