Identify required work to support SLP tokens

[haplo]

Research what changes are necessary for full SLP support and create new issues splitting the work in smaller tasks. Each task should make sense on its own, i.e. it should be useful after it's completed, even if it doesn't cover all use cases.

https://simpleledger.cash/get-started/
https://slp.dev/

[haplo]

Probably start by adding support for SLP Token Type 1.