Add video targeting to Beachfront adapter

[jsalis]

Type of change

• Feature
• Does this change affect user-facing APIs or examples documented on http://prebid.org?

Description of change

Adds properties to the video bid request, and a bid param to override supported mime types.

{
  bidder: 'beachfront',
  params: {
    bidfloor: 0.01,
    appId: '3b16770b-17af-4d22-daff-9606bdf2c9c3'
    video: {
      mimes: ['video/mp4', 'application/javascript']
    }
  }
}

prebid/prebid.github.io#687

[jsalis]

Added PR for docs