[ecash-wallet] Support for GENESIS, SEND, MINT, and BURN for SLP_TOKEN_TYPE_NFT1_GROUP

Summary: Add basic functionality for SLP group tokens. This is identical to SLP FUNGIBLE, except we call thle functions with a different token type. The real work here will be when we support minting the child NFTs.

Test Plan: npm test, CI tests, proofread README updates

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18551