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.
