Store types (with autoincrement ID) using big endian for ordering

[lumtis]

Use big-endian utility function fromencoding/binary to store the type scaffolding from its ID so that these are stored in the correct order inside the IAVL

Example with proposal here: https://github.com/cosmos/cosmos-sdk/blob/master/x/gov/keeper/proposal.go

We can also use uint64 instead of string for the id type id depends how convenient it is for the developer