Lack of some node interaction functions

[automainint]

Lack of some node interaction functions:

• assets/balance (by account address),
• assets/nft,
• etc.

Need this to get list of token balances and list of NFTs by account address.

Workaround is to make a direct REST request to node by API_BASE URL.
I noticed, Waves Keeper doing direct REST requests while also depending on waves-transactions, which seems not very efficient.