[Pharo-project] Issue 1754 ready to integrate

http://code.google.com/p/pharo/issues/detail?id=1754 There is a functionaluty in ImageSegment to discover used and unused classes. That has nothing to do and should be in ImageSegment. Stuff to be cleaned: ImageSegment >> activeClasses ImageSegment >> discoverActiveClasses ImageSegment >> swapOutInactiveClasses ImageSegment >> activeClassesByCategory Behavior >> induceMDFault Behavior >> recoverFromMDFaultWithTrace Behavior >> recoverFromMDFault