Associate meetings with recordings

When a recording is created it tries to find the BigbluebuttonMeeting instance
that created the recording and associates it with the recording.

refs #1032
Use MysQL as default in development and testing

Discovered a few issues when querying for datetime attributes in sqlite3.
Switched to MySQL because of it and because it is the database already being
used in Mconf-Web, hence the database recommended for BigbluebuttonRails.

refs #1032
Add a few missing strings to the locale

They are used in Bigbluebutton::RoomsController#external_auth.