* Add custom CSS field to config
This allows users to set/customize an instance's theme and appearance to
their liking. The config CSS field is prepopulated with all default CSS
variable values to allow quick editing.
Note that this can be somewhat of a "footgun" if someone updates the
CSS to hide all fields/search/etc. Should probably add some sort of
bandaid "admin" feature for public instances to employ until the whole
cookie/session issue is investigated further.
* Symlink all app static files to test dir
* Refactor app/misc/*.json -> app/static/settings/*.json
The country/language json files are used for user config settings, so
the "misc" name didn't really make sense. Also moved these to the static
folder to make testing easier.
* Fix light theme variables in dark theme css
* Minor style tweaking
