Extend Tagger event class

For a more flexible use of the Tagger class, which is defined in Event/PhysEvent/xml/Tagger.xml and holds the flavour tagging result for one tagging algorithm, following changes have been made:

• extend the number of available TaggerType values (enum)
  • the "old" TaggerType values are now explicitly matched to an integer value
  • new TaggerType values have been added with a numbering scheme that allows to easily add new tagging algorithms for testing, development, etc.
• the strTypConv functionality of the GOD enums has been enabled
• two new members have been added to allow for recalculating the mistag probability and tagging decision without having to rerun the tagging
  • the mva output value of the tagging algorithm
  • the charge observable of the tagging algorithm (e.g. the charge of the tagging particle or the weighted charge of the secondary vertex of the OS b)

These changes to Tagger.xml also implied changes in the PackedFlavourTag and PackedTagger classes.