Adds equivalent qualifier for XPath locator
Adds capability to share stored values across tests (test executers)
Adds generic string substitution with stored var values

- implements Selenium RC-style ${varname} variable substitution method
- variables are now substituted in the open() method
Adds 'type' and 'sendKeys' as aliases to 'typeKeys'
Adds emulation of "fireEvent blur" and "fireEvent focus"

- Adds limited emulation of Selenium RC's fireEvent blur and focus.
- blur works by sending TAB key, so might not work on elements that are not of type input