Use the slip44 derivation path for mnemonic key derivation

[joeabbey]

There's a quasi-standard method of HD-wallet derivation https://interchain-io.medium.com/cosmos-derivation-path-spec-proposal-completed-5fea6fe87e12

For us to avoid surprising people, lens should use the slip44 cointype

Many of the chain-registry entries have the cointype in their chain.json

For example:

thorchain/chain.json

    "node_home": "$HOME/.thornode",
    "slip44": 931,
    "genesis": {