Make possible to install Cycles Ledger on local net, without full NNS

[vporton]

It is important for debugging to install Cycles Ledger (or its stripped down mockup) on local network, without installing full NNS.

As an attempted workaround, I created my own mock Cycles Ledger canister, but my mock ledger is sadly not synchronized to actual spendings and transfers of cycles.

[raymondk]

We are working on a feature in pocket-ic that will allow you to start pocket-ic with some "features" - having a ledger is one of them.