loader: change playback priority to always load html5 playback for safari
html5 video: improve playback type checking to infer whether a hls stream is live or vod
html5 video: add update settings call after loading metadata to update the media control accordingly
add enabled status to ui container plugin
background button: add enabled state check to show/hide media control play button
spinner: rename plugin to make it easier to override the plugin externally
ui core plugin: add enable/disable methods
media control: add is visible method to allow plugins to check its status
background button: add player option to toggle displaying the button without disabling the plugin