Rotala

[Calum]

Exchange module needs another rework:

• Will need to mirror exchange package so we hit feature parity.
• Switch RPC to JSON.
• Server bin.
• Provide a test env.
• Clock dependency should be limited to rotala, when you init an exchange it should you tell what the period start and frequency.
• Should rename existing exchanges.
• Name original exchange api too: insert, delete, modify, cancel may change in future so this needs to be named.
• Add docs.
• Should further cut down on code within original alator. Purpose of this package is to really act as a client for exchange so the broker/strategy impls are just examples.
• Data store for rotala should be file, but this is something that could change in future. So load stage has to be defined for server.