Document locking order of class IdentityFetcher:
- We always lock the WOT first because its objects (Identity, Trust, Score) are the base objects for everything else.
- The order between IntroductionPuzzleStore and IdentityFetcher is defined by the current code in class IntroductionServer. Its onSuccess() first locks the puzzlestore and then uses XMLTransformer.importIntroduction() which locks the IdentityFetcher
- The database can always be locked last when we actually start modifying stuff.