As said before; `lib_ledger` was meant to be a general abstraction to
any underlying CLI ledger.
But, between C++ `ledger` and Ledger Hardware Wallet, this abstraction
has become too confusing and counterproductive.
Since `hledger` will be the underlying implementation for the forseeable
future, all doubt should now be removed.
- Generates new custom plugin directory layout upon `gen`
* Allows for drop-in client-side/container-side custom plugins
- Moved container plugin example into container's plugins
* Plugin is no longer generated upon `gen` (it's available in-repo)
- Updates plugin example
- Provides requisite lib_finance initialization
- Refactored, added more checks
- Expand example case
- Linter fixes
