Deleted legacy client themes.

bigbluebutton-client/branding/default/build.xml

bigbluebutton-client/branding/default/style/css/BBBBlack.css

...uebutton-client/branding/default/style/css/BBBDefault.css

bigbluebutton-client/branding/default/style/css/V2Theme.css

...randing/default/style/css/assets/images/3_closeButton.png

...ding/default/style/css/assets/images/3_decreaseButton.png

...ding/default/style/css/assets/images/3_increaseButton.png

...ding/default/style/css/assets/images/3_minimizeButton.png

...lt/style/css/assets/images/almost_strong_audio_status.png

...ault/style/css/assets/images/almost_weak_audio_status.png

...ding/default/style/css/assets/images/arrows_redo_icon.png

...default/style/css/assets/images/arrows_redo_icon_grey.png

...ding/default/style/css/assets/images/arrows_undo_icon.png

...default/style/css/assets/images/arrows_undo_icon_grey.png

...anding/default/style/css/assets/images/audio_20_white.png

...anding/default/style/css/assets/images/audio_20_white.xcf

.../default/style/css/assets/images/audio_muted_20_white.png

...nt/branding/default/style/css/assets/images/bandwidth.png

...efault/style/css/assets/images/bbb_accept_certificate.png

...nding/default/style/css/assets/images/bbb_empty_image.png