Merge branch 'plain-bg' into 'develop'

CHANGELOG.md

src/App.js

src/App.scss

src/App.vue

src/components/desktop_nav/desktop_nav.scss

src/components/settings_modal/tabs/general_tab.js

src/components/settings_modal/tabs/general_tab.vue

src/components/settings_modal/tabs/theme_tab/theme_tab.scss

src/components/settings_modal/tabs/theme_tab/theme_tab.vue

src/i18n/en.json

src/modules/config.js

src/services/theme_data/pleromafe.js

static/themes/redmond-xx-se.json

static/themes/redmond-xx.json

static/themes/redmond-xxi.json