[brightcove] Improve the 'experienceJSON' regex (#3081)

One of the strings may contain ';', we would get an invalid json string.
[brightcove] Add support for renditions with 'remote' set to True (fixes #3081)

The url needs to be modified to get the flv video.
[brightcove] Modernize some tests
[brightcove] Set the filesize of the formats and use _sort_formats