scaffold storage module for SDK

[martyall]

The storage module is arguably the most important part, it's responsible for keeping track of authenticated application state, communicating state hashes, staging and running transactions.

We would like a few options here for implementations

• an in memory option https://github.com/kadena-io/merkle-log
• a "webscale" persisted option (leading contender is https://github.com/google/trillian

This involves a bit of research to figure out what the minimal surface area is between the storage layer and the ABCI server

• querying state
• communicating application hash
• staging a tx (CheckTx)
• running a tx (RunTx)

but this needs an actual specification.

[martyall]

note that until kadena-io/merkle-log#2 is resolved we cannot use the kadena package

[martyall]

here's another in memory example https://github.com/oscoin/avl-auth

[martyall]

https://github.com/enzoh/dfinity-radix-tree

https://github.com/enzoh/dfinity-radix-tree/blob/6a1d1675ba185c12663d7e9a67720b0e98850f7d/src/DFINITY/RadixTree/Types.hs#L54-L68