Branding back to BigBlueButton and adding back some of the client images we removed. This need to be reviewed to avoid having all this unused images!

- using localization resources for the names defined on config.xml
- green background on succeeded tests
- "Succeeded" string as result of succeeded tests

improved the client check so now it uses sip.js and bbb_webrtc_bridge_sip.js from the bigbluebutton-client, so it's going to be easier to maintain; included some new callbacks on bigbluebutton-client related to the websockets; just after the webrtc test, the connection is closed

fixed the sip test changed since the last pull request, also adding more details when a rtmp connection is not successfully established

using a bigger image for the download test; providing immediate feedback about the download speed for the user, with incremental changes; reduced the precision of the ping test; set the mail button to open the client e-mail on a blank page