Allow user to force a specific HLS bitrate to record.  Right now there is no

UI to make this easy, and I have mostly used it as a debugging tool.

To use this, the channel and iptv_channel tables need to be updated.

In the channel table, create a separate channel entry for each bitrate.  In other
words, instead of just having a SKYNEWS channel and allowing myth to auto
select the best bitrate for the available bandwidth, create three separate
SKYNEWS channels:  SKYNEWS-1, SKYNEWS-2, SKYNEWS-3.

INSERT INTO `channel` (`chanid`, `channum`, `freqid`, `sourceid`,
`callsign`, `name`, `icon`, `finetune`, `videofilters`, `xmltvid`,
`recpriority`, `contrast`, `brightness`, `colour`, `hue`, `tvformat`,
`visible`, `outputfilters`, `useonairguide`, `mplexid`, `serviceid`,
`tmoffset`, `atsc_major_chan`, `atsc_minor_chan`, `last_record`,
`default_authority`, `commmethod`, `iptvid`) VALUES
(5051,'5-1',NULL,5,'SKYNEWS-1','SKYNEWS-1','',NULL,'','19572',0,32768,32768,32768,32768,'Default',1,'',0,NULL,0,0,0,0,'2014-02-20 21:40:47','',-1,NULL),
(5052,'5-2',NULL,5,'SKYNEWS-2','SKYNEWS-2','',NULL,'','19572',0,32768,32768,32768,32768,'Default',1,'',0,NULL,0,0,0,0,'2014-02-20 21:40:47','',-1,NULL),
(5053,'5-3',NULL,5,'SKYNEWS-3','SKYNEWS-3','',NULL,'','19572',0,32768,32768,32768,32768,'Default',1,'',0,NULL,0,0,0,0,'2014-02-20
21:40:47','',-1,NULL);

In the iptv_channel table, also create a separate channel entry for each
bitrate, and set the 'bitrate' column to be the index of the desired
bitrate.

INSERT INTO `iptv_channel` (`chanid`, `url`, `type`, `bitrate`)
VALUES
(5051,'http://skynews-1.ml.llnwd.net/skynews_sd/smil:mbr_alpha.smil/playlist.m3u8','data',1),
(5052,'http://skynews-1.ml.llnwd.net/skynews_sd/smil:mbr_alpha.smil/playlist.m3u8','data',2),
(5053,'http://skynews-1.ml.llnwd.net/skynews_sd/smil:mbr_alpha.smil/playlist.m3u8','data',3);

I may change this from using an index to the actual desired bitrate.  If the
feed suddenly changes the bitrates they offer, though, that could cause it
to suddenly stop working.

If users find value in being able to select a specific bitrate, a UI will
have to be developed.

(cherry picked from commit 391bf8f2d619b3a3d1d87c2e351169838408e2e9)