ImproveDigital bid adapter GDPR support

[jbartek25]

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 support for Prebid ConsentManagement module into ImproveDigital bid adapter + minor internal changes

• contact email of the adapter’s maintainer: j.bartek@improvedigital.com, hb@improvedigital.com
• official adapter submission

For any changes that affect user-facing APIs or example code documented on http://prebid.org, please provide:

• A link to a PR on the docs repo at https://github.com/prebid/prebid.github.io/
  Adding GDPR support prebid.github.io#788

Other information

Our adapter doesn't need to handle user syncs in any special way for GDPR

[snapwich]

This adapter should be updated to use spec.getUserSyncs on the bidderFactory rather than userSync.registerSync directly. I won't block this pull-request so we can get the GDPR stuff through, but this change should be made in the future.