Add brt mode to reverse byte order

[vovac12]

Closes #281

[ikopylov]

Byte order reversion is essentially a migration from BLOB version 1 to version 2. Therefore, I propose to implement the migration semantic in this request:

1. The command must be named migrate
2. Target version must be passed as a parameter (if not specified, migrate to the latest)
3. Migration logic should get starting version from BLOB file itself
4. Migration logic should apply migrations sequentially from the starting version to the ending