Override page object methods to log the actions taken by the methods
before or after the action, as appropriate.

Allow page object action logging to be turned on via a QA_DEBUG env var.
Unlike CHROME_HEADLESS (and the soon to arrive VERBOSE), QA_DEBUG
is false by default.

QA_DEBUG is used instead of just DEBUG because that enables Selenium
debug logging.

Mask passwords entered into fields with a QA selector with 'password'
in the name. Doesn't mask sensitive data entered into any other field.