FEATURE: Site settings defaults per locale

This change-set allows setting different defaults for different locales. 

It also:

- Adds extensive testing around site setting validation

- raises deprecation error if site setting has the default property based on env

- relocated site settings for dev and tests in the initializer

- deprecated client_setting in the site setting's loading process

- ensure it raises when a enum site setting being set

- default_locale is promoted to `required` category.

- fixes incorrect default setting and validation

- fixes ensure type check for site settings

- creates a benchmark for site setting

- sets reasonable defaults for Chinese

spec/controllers/admin/site_settings_controller_spec.rb

@@ -27,6 +27,7 @@ describe Admin::SiteSettingsController do
 
       before do
         SiteSetting.setting(:test_setting, "default")
+        SiteSetting.refresh!
       end
 
       it 'sets the value when the param is present' do
@@ -49,6 +50,7 @@ describe Admin::SiteSettingsController do
 
       it 'does not allow changing of hidden settings' do
         SiteSetting.setting(:hidden_setting, "hidden", hidden: true)
+        SiteSetting.refresh!
         result = xhr :put, :update, id: 'hidden_setting', hidden_setting: 'not allowed'
         expect(SiteSetting.hidden_setting).to eq("hidden")
         expect(result.status).to eq(422)