Incorrect mapping for user agent and performance timing contexts

[sphinks]

I have faced a problem with snowplow model in DBT:

Database Error in model snowplow_web_timing_context (models/page_views/optional/snowplow_web_timing_context.sql)
  column "event_id" specified in USING clause does not exist in left table
  compiled SQL at target/compiled/snowplow/page_views/optional/snowplow_web_timing_context.sql

I'm using for timing context just standart context: https://github.com/snowplow/snowplow/wiki/1-General-parameters-for-the-Javascript-tracker#performanceTiming with schema https://github.com/snowplow/iglu-central/blob/master/sql/org.w3/performance_timing_1.sql
I suspect there is a bug of using event_id as key for join, because in schema used root_id as reference to event. Also, here I see an example of processing timing: https://discourse.snowplowanalytics.com/t/measuring-page-load-times-with-the-performance-timing-context-tutorial/100 and it is done with root_id.

There is one more issue: not existing field page_view_id, I suspect that not optional views were amended accroding to new field name: https://github.com/fishtown-analytics/snowplow/blob/274c7969d61a552cdc996d00801d7f43cc9b6c03/macros/adapters/default/page_views/snowplow_web_page_context.sql#L35 In optional view it was not changed, so they still use page_view_id, not just id.

[sphinks]

@drewbanin I'm going to test my fix and if it will be ok, make a PR.

[sphinks]

@drewbanin please, check #41