1233 replicator: rename columns via updatable views

[gabrielwol]

What this pull request accomplishes:

• Pulls in updates from bdit_dag_utils which allow use of an updatable VIEW instead of a TABLE as the destination for replication. This change allows us to adjust column names for data coming in to bigdata.
• update readme
• move replicators airflow variable to local import (save dynamic definitions for mapped tasks!)
• To be reviewed in tandem with 13 add view insert functionality to copy table bdit_dag_utils#14
• Commit all the traffic & traffic_staging tables/views (moved to 1246 commit all traffic and traffic staging replication objects #1247)

Issue(s) this solves:

• Rename centreline2 columns in bigdata #1233

What, in particular, needs to reviewed:

What needs to be done by a sysadmin after this PR is merged

E.g.: these tables need to be migrated/created in the production schema.

[gabrielwol]

We are questioning whether we should scrap this PR and instead just tell people to use the views, which allow more flexibility beyond column renaming (like separating centreline_id / centreline_type).