Final classes moved to serenity_bdd and Serenity prefix names

This should be merged after 'big_move' branch.
This moves the final items in jbehave project to serenity_bdd package name, and class prefix of Serenity.
Created deprecated version of Metafilter, and ensured that serenity_bdd package takes precedence over thucydides package Metafilter.