change level indicator color. remove border on audio icons

src/assets/images/dropdown_arrow.png

src/assets/images/dropdown_arrow@2x.png

src/assets/images/level_background.png

src/assets/images/level_background@2x.png

src/assets/images/level_fill.png

src/assets/images/level_fill@2x.png

src/assets/images/mic_level.png

src/assets/images/mic_level@2x.png

src/assets/images/speaker_level.png

src/assets/images/speaker_level@2x.png

src/assets/stylesheets/audio.scss

src/react-components/ui-root.js