Schemachange

Added
- Added a new optional parameter `--query-tag` to append a string to the QUERY_TAG that is attached to every SQL statement executed

Added
- Added filtering of secrets when vars are displayed on the console.
- Added filtering of secrets for deploy command when SQL statements are displayed as part of verbose output.

Changed
- Changed vars to be pretty printed to the console.
- Changed demo citibike_jinja to demonstrate secret filtering.
- Updated the Jinja templating engine section of the README.md to document Jinja autoescaping status and added warning about untrusted input.
- Updated the table of contents section of the README.md to included missing sections.

Changed
- Added `env_var` Jinja function support to migration templates.
- Backed out Jinja autoescape change from 3.3.2. The default is now to have it disabled (using autoescape=False).

Changed
- Configured Jinja to escape inputs to templates (using autoescape=True). This helps protect rendered templates against XSS and other vulnerabilities

Changed
- Project is now configured with setup.cfg. There should be no change to package users.

Added
- Added processing of schemachange-config.yml with jinja templating engine.
- Included new Jinja function env_var for accessing environmental variables from the config file.