This changeset allows for history and bookmark observers to be registered via
the category manager. This means the bookmarks service does not have to be
initialized at startup to register observers with it, as well as the history
service.
r=sdwilsh
r=mak
r=dietrich
Bug 476300 - Calculate all page frecencies when upgrading/migrating
Bug 482351 - 1 sort operation required by mDBInvalidFrecencies
Create a new method FixInvalidFrecencies that finds invalid (negative) frecencies and recalculates them. Use it for handling creating/migrating DBs as well as recalculating invalid places on daily idle (place frecencies are already estimated by decay). This obviates a few preferences, queries and methods related to recalculating on idle. The test uses mork history with a number of pages that now all get their frecencies calculated on migrate, where before this fix, the test fails with a bunch of pages still with negative frecencies.
