Apacdex Bid Adapter: add placementId param and optimize payload data

[thuyhq]

Type of change

• Bugfix
• Feature
• New bidder adapter
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Does this change affect user-facing APIs or examples documented on http://prebid.org?
• Other

Description of change

• Adding the "placementId" parameter.

{
  bidder: 'apacdex',
  params: {
    placementId: "1132138",
    floorPrice: 0.01
  }
}

• We also reduce some unused data when sending to our endpoint.