[Pharo-project] Preparing 1.4 beta

Hi since we will not have OPAL as preview in 1.4 and we do not need to change the refactoring engine code, we will unload AST and RBEngine package from the system and start to pass in 1.4 beta probably at the end of the month. One idea was that we could have decent tools to work on the core but this is not the case. We will encourage people to try their packages to 1.4 beta and rc so that we can produce 1.4. Stef