* partially done alternate migration scheme
* finish altering migration framework
* migrate tests to new migration framework
* address comments
* remove superfluous newline
[ci skip]
* TempIdx -> TempIndex
[ci skip]
* modify account_db to work on address hash, not address
* add a database migration for new accountdb
* preserve first 96 bits of keys when combining
* handle metadata keys in migration and preserve first 96 bits
* fix comments and hash address instead of hash
* different migrations based on pruning
* migrations mutably borrow self
* batch abstraction for migration
* added missing licence headers
* overlay recent v7 migration
* better error handling, migrate version key as well
* fix migration tests
* commit final batch and migrate journaled insertions
* two passes on journal to migrate all possible deleted keys
