add dao which takes care about all CRUD operations on storage
remove blockchain state since everything is stored on change
remove storage operations from structs(entities)
move structs to entities package
commit methods duplicated putSmthIntoStore functions, but have MemCachedStore
now that can easily substitute for a Batch, especially given that interop
needs something like that for its storage purposes anyway.
Linter isn't happy with our recent changes:
pkg/core/contract_state.go:109:1: receiver name cs should be consistent with previous receiver name a for ContractState
pkg/core/contract_state.go:114:1: receiver name cs should be consistent with previous receiver name a for ContractState
pkg/core/contract_state.go:119:1: receiver name cs should be consistent with previous receiver name a for ContractState
But actually `a` here most probably is a copy-paste from AssetState methods,
so fit the old code to match the new one.
PublishTX only had one of these flags, but newer contracts (created via the
interop function) can have more and these flags are aggregated into one field
that uses PropertyState enumeration (it's used to publish contract, so
supposedly it's also a nice choice for contract state storage).
