Fix issues on certain hbb tvs

Switch from using display:none to visibility:hidden when hiding the broadcast tv object to prevent the object getting cleaned up before it should.
Support the .item() accessor for the channel list to cater for devices that don't support the array accessor syntax.
Merge branch 'master' into hbbtvsource-display-and-channellist-fixes
Merge branch 'master' into hbbtvsource-display-and-channellist-fixes
Merge pull request #159 from fmtvp/hbbtvsource-display-and-channellist-fixes

Hbbtvsource display and channellist fixes