poll slot renamed, lightBg customization implemented

src/App.scss

src/components/autosuggest/autosuggest.vue

src/components/dialog_modal/dialog_modal.vue

src/components/emoji_input/emoji_input.vue

src/components/nav_panel/nav_panel.vue

src/components/selectable_list/selectable_list.vue

src/components/side_drawer/side_drawer.vue

src/components/status/status.vue

src/components/style_switcher/style_switcher.vue

src/services/style_setter/style_setter.js

src/services/theme_data/theme_data.service.js