Feature request - expose some of the indy ledger browser functions through the admin api

[ianco]

indy-sdk has some support for reading arbitrary ledger transactions, see: https://github.com/hyperledger/indy-sdk/blob/master/libindy/src/api/ledger.rs aca-py uses some of these functions internally but doesn't expose any of them through its api would probably be useful to expose "get schema", "get cred_def", "get transaction" to allow aca-py users to read ledger info for example if an issuer knows a schema id and wants to confirm what is registered on the ledger, how can they (currently) look this up? or if they want to confirm what's recorded on the ledger for their cred def? (or if they just want to do some ad-hoc ledger browsing?)