massively improved initial theme loading code, added checks and warnings when

src/boot/after_store.js

src/components/style_switcher/style_switcher.js

src/components/style_switcher/style_switcher.scss

src/components/style_switcher/style_switcher.vue

src/i18n/en.json

src/modules/config.js

src/modules/instance.js

src/services/style_setter/style_setter.js