Sync local PolicyContract with remote network

[ixje]

There is a use-case where you'd like your local environment to match e.g. MainNet in terms of fees (storage/execution prices) such that you can develop your contract to fit within allowed max GAS usage requirements.

This idea would add an inline button on the PolicyContract (in the contracts panel) to sync the remote policy to the local chain. We have 2 approaches

1. use the RPC method invokefunction on the PolicyContract and request GetFeePerByte, GetExecFeeFactor and GetStoragePrice
2. use RPC servers with the StateService plugin as we know all keys to request.

[ixje]

Just learned there is a policy sync command in neoxpress. So this is just a matter of presenting it in the UI