RF-13777: Graphene upgraded to 2.1.0.Alpha1

-RF Screenshooter commented out, it will be replaced with Graphene screenshooter soon
RF-13777: Custom RF screenshooter deleted

-screenshoting mechanism is now provided by Graphene itself
-profile take-screenshots added, it just needs to he on the classpath in order to take screenshots
-default setting is that it takes screenshots only when test fails, can be changed in arquillian.xml
RF-13777: TESTS.md updated with screenshots possibility
Merge pull request #101 from richfaces/RF-13777

RF-13777: Graphene upgraded to 2.1.0.Alpha1