The implementation of categories is now synchronization safe

Code cleanup:
 - The Format Manager implementation is now split between two files: FormatClasses.{h|cpp} where the
   actual formatter classes (ValueFormat, SummaryFormat, ...) are implemented and
   FormatManager.{h|cpp} where the infrastructure classes (FormatNavigator, FormatManager, ...)
   are contained. The wrapper code always remains in Debugger.{h|cpp}
 - Several leftover fields, methods and comments from previous design choices have been removed
type category subcommands (enable, disable, delete) now can take a list of category names as input
 - for type category enable, saying "enable A B C" is the same as saying
    enable C
    enable B
    enable A
   (the ordering is relevant in enabling categories, and it is expected that a user typing
    enable A B C wants to look into category A, then into B, then into C and not the other
    way round)
 - for the other two commands, the order is not really relevant (however, the same inverted ordering
   is used for consistency)

llvm-svn: 135494