CSS (default skin) is not loaded in clean DB

A new installation of the site no longer loads any CSS due to not having a default_skin_id set in the AdminSettings. I suspect caused by where default settings were changed but not codified in DB initialization scripts or startup rake tasks.

Reproduce:

1. Run reset_database.sh (or rebuild environment completely)

2. Navigate to the dev site, note that no CSS is displayed

3. Verify via DB or rails console that default_skin_id is null in AdminSettings

Workaround is to set the default_skin_id either via rails console or just directly in the DB (remember to clear cache).

Suggestion from @tickinginstant:

It seems like it'd be cleaner to set it as part of the skins:load_site_skins task, which is run in the script/reset_database.sh script (which I believe is used by docker). I think it might work to add something like this to the task: