ljelinkova_Fix screenshot issues

This file name is not good for a screenshot file ./target/screenshots/org.jboss.reddeer.junit.extension.after.test.impl.CloseAllShellsExt-runAfterTest.png. It probably can get overwritten by many failing tests. Screenshot file should contain name of failed test

See master job RedDeer_master_matrix/jdk=sunjdk1.7,label=fenix/322/consoleText

It seems to create too many screenshots for one test fail but I'm not absolutely sure about it. Please check it.

Screenshots has to be created also for failures in BeforeClass a AfterClass methods.

Do not overwrite screen shots files generate unique file names instead