ARQGRA-258: enrichment supports classes wrapping web elements

* Page fragment enricher doesn't throw an exception when it meets
  field with abstract type or type with non empty constructor.
  It skips these fields instead of throwing an exception.

* Added a new enricher which is able to inject fiels with @FindBy
  annotation and type with constructor requiring web element.

* Unfortunately the new enrichment can't be used for injecting
  fields with type org.openqa.selenium.support.ui.Select, because
  the Select class accesses to the web element in its constructor
  and the web element isn't available yet (page is not loaded for
  example).