…id.events

Missing timestamp (waiting for prebid#1584)

- wurl insertion in cached bids
- vast modifying in video bids

This avoids unnecessary conversions between json and string

ok  	github.com/prebid/prebid-server/endpoints/events	0.034s	coverage: 96.1% of statements

- Fixed comments
- Removed redundant types in func proto
- Add bool parameter to `ModifyVastXmlString()` to indicate string was changed
- Decode RawMessage instead of casting to string (to handle encoded escapes)

> ok github.com/prebid/prebid-server/endpoints/events	0.039s	coverage: 97.4% of statements

When the VAST is modified to insert the event tracking tag,
the modified creative is also returned in the bid response, in addition to being cached.

Behavior currently implemented requires targeting enabled.

Also renamed eventsData->eventTracking

- all bids have vast modified if account and bidder enabled, not just winning
- all NON-VIDEO bids have events if account or request enabled
- all cached NON-VIDEO bids have wurl patched in if account or request enabled.

prebid#1015 (comment)

prebid#1015 (comment)

- all VIDEO bids, cached and returned, have modified VAST if account and bidder enabled - not just winning cached bids.
- all NON-VIDEO returned bids have `ext.prebid.events` if account or request enabled
- all cached NON-VIDEO bids have `wurl` patched in if account or request enabled.

VAST is modified if *either* account or request setting demanded it.

prebid#1015 (comment)

# Conflicts:
#	exchange/exchange.go
#	exchange/exchange_test.go

prebid#1597 (comment)

prebid#1597 (comment)

prebid#1597 (comment)

Address prebid#1597 (comment)

Addresses prebid#1597 (comment)

prebid#1597 (comment)

# Conflicts:
#	openrtb_ext/request.go