services/horizon: Include command to reach each migration in horizon db migrate status

[paulbellamy]

@2opremio: I think that for the migrate status command it would be really useful for each row to also print what migrate down/up COUNT command is needed to get there. I can create a separate ticket for that if you prefer.

#3737 (comment)

What alternatives are there?

Change horizon db migrate to horizon db sync [version] which does the migrations to reach a given version deployed. This would be more useful, but harder to implement.