Add playlists feature (#871)

* Open multi-file torrents as playlists

* Add `repeat` and `shuffle` options to the player

* Autoplay first file in torrent

* replaces `pickFileToPlay` feature
* when reopening player, restores the most recently viewed file

* Add playlist navigation buttons to Windows thumbar

* Remove `repeat` and `shuffle` options

This reverts commit 9284122461.

* Play files in order they appear in torrent

* Clean up playlists code

src/renderer/controllers/media-controller.js

@@ -2,6 +2,8 @@ const electron = require('electron')
 
 const ipcRenderer = electron.ipcRenderer
 
+const Playlist = require('../lib/playlist')
+
 // Controls local play back: the <video>/<audio> tag and VLC
 // Does not control remote casting (Chromecast etc)
 module.exports = class MediaController {
@@ -44,7 +46,8 @@ module.exports = class MediaController {
 
   openExternalPlayer () {
     var state = this.state
-    ipcRenderer.send('openExternalPlayer', state.saved.prefs.externalPlayerPath, state.server.localURL, state.window.title)
+    var mediaURL = Playlist.getCurrentLocalURL(this.state)
+    ipcRenderer.send('openExternalPlayer', state.saved.prefs.externalPlayerPath, mediaURL, state.window.title)
     state.playing.location = 'external'
   }