Ethereum provider initialization

[Shadowfiend]

Allow the application to connect to the Ethereum network and receive back a chain.Provider implementor. chain.Provider is currently defined as chain.Handle:

https://github.com/keep-network/keep-core/blob/90979a076d259a26c1ee7fe7a175350106f2c3cd/pkg/chain/chain.go#L22-L28

[Shadowfiend]

This will probably look like:

import "github.com/keep-network/keep-core/pkg/chain/ethereum"
...
  provider := ethereum.Connect(config)

And config will be an ethereum.Config object.

[pschlump]

PR #103 addresses this and is merge.