Refactor: Move ledger code to its own subfolder

[ValarDragon]

Summary

Currently there are 5 files related to the ledger in /crypto. A minor change that I think improves overall codestructure would be to move all of these to their own subfolder /crypto/ledger.

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[fedekunze]

cc: @alessio

[alessio]

IMHO Ledger-related amount of code is too small for it to justify the creation of another directory (ref: https://about.sourcegraph.com/go/idiomatic-go#tiny-package-syndrome)

[ValarDragon]

The point of the tiny-package syndrome was to argue that 1-2 file large packages aren't a great idea in some cases.

Here the ledger code is the majority of the directory, which is unexpected functionality imo of this top level dir. Its responsiblity at the moment is Handling encoding of things to disk (armor*.go), handling encoding of go objects for the sub-directories (amino.go, test_encoding.go), explaining what its sub-directories do (bcrypt_readme), and oddly handling all ledger logic.

Feels like packaging the ledger logic is good for modularity, but its up to the repo maintainers.

[alessio]

OK, I think you have a point @ValarDragon. I'll take care of the migration shortly

[ValarDragon]

Thanks!