Load playlist with initial video at specified index or no starting video

[mister-ben]

Description

Allows the starting index of a playlist to be specified to load a video other than [0] into the player, or no video.
Use cases:

• Playlists that should start on a "featured" item which is not first in the list
• Facilitates direct linking
• Playlists that do not include the content currently playing, e.g. related videos
• Loaded new playlists without interrupting currently playback, e.g. a category tabs UI

Example: http://jsbin.com/diyove/edit?html,output

Specific Changes proposed

playlist() takes an additional Number argument for the starting index, defaulting to 0 if not specified. When the playlist is loaded currentItem() is used instead of first(). An index of -1 results in playlist loaded but no video from the playlist loaded into the player.

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Unit Tests updated or fixed
  • Docs/guides updated
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

[gkatsev]

LGTM.