FEATURE: Theme settings (2) (#5611)

Allows theme authors to specify custom theme settings for the theme. 

Centralizes the theme/site settings into a single construct

app/models/remote_theme.rb

@@ -76,6 +76,8 @@ class RemoteTheme < ActiveRecord::Base
     end
 
     Theme.targets.keys.each do |target|
+      next if target == :settings
+
       ALLOWED_FIELDS.each do |field|
         lookup =
           if field == "scss"
@@ -91,6 +93,9 @@ class RemoteTheme < ActiveRecord::Base
       end
     end
 
+    settings_yaml = importer["settings.yaml"] || importer["settings.yml"]
+    theme.set_field(target: :settings, name: "yaml", value: settings_yaml)
+
     self.license_url ||= theme_info["license_url"]
     self.about_url ||= theme_info["about_url"]
     self.remote_updated_at = Time.zone.now