Simplify the migration system.
Simplify the migration system.

LLC-116

LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core