Add performance report feature

[slawekradzyminski]

Dependends on #715

FluentLenium can create performance report on demand (via configuration) in tests.

[picimako]

Based (partially) on the discussion with @slawekradzyminski here is a summary of the performance reporting:

• create custom performance report (by default in HTML format). Consider other formats like JSON and XML (to provide the options for enduser to make custom reporting)
• update performance report when url changes in the browser
  -- related documents:
  --- https://stackoverflow.com/questions/3522090/event-when-window-location-href-changes/33668370
  --- https://developer.mozilla.org/en-US/docs/Web/API/WindowEventHandlers/onbeforeunload
  -- anchor and ajax based changes are probably out of scope
  -- need to check what to do when there is a non-anchor URL change but there is no actual navigation
• the format of the report is up for discussion
• it should a switchable, on demand feature, via configuration
• consider creating a separate maven module for this