Add authentication specific actions to scripts

Add the following auth step actions to engine:

Method auth.successIfAtURL(urlPattern)

Authentication is successful if the current page matches.

Arguments:

• urlPattern string -- URL or regex

Method auth.successIfElementFound(selector)

Authentication is successful if an element is found on current page.

Arguments:

• Selector string -- Selector for item indicating authentication was successful

auth.failedIfAtURL(urlPattern)

Authentication failed if at URL.

Arguments:

• urlPattern string -- URL or regex

Method auth.failedIfElementFound(selector)

Authentication failed if an element is found on current page.

Arguments:

• Selector string -- Selector for item indicating authentication failed