substrate implementation

[Ivshti]

Considering we already have Ethereum and Cosmos implementations here:
https://github.com/AdExNetwork/adex-protocol-eth
https://github.com/AdExNetwork/adex-protocol-cosmos

The next step will be a substrate implementation:

THIS BELOW IS OUTDATED; see https://github.com/adexnetwork/adex-protocol-substrate

A brief look into https://github.com/paritytech/substrate/blob/master/srml/example/src/lib.rs shows that we need to:

• port the types from the go implementation in cosmos to rust
• decl_module for bid_cancel, commitment_start and commitment_finalize
• use let sender = ensure_signed(origin)? for bid_cancel and commitment_start, since those need to be invoked by respecitvely the demand (advertiser) and supply (publisher)
• use on_finalise to do cleanup, i.e. timed out commitments
• everything should emit an event, so decl_event for each one
• the substrate storage should make our job pretty straight forward when it comes to storing things