Refactoring of Code

[nisdas]

It was agreed by the team in #60 to refactor the code in order to prevent duplication of code and for easier testing.
The objectives of this PR are to

• Abstract all common methods into a common interface which would be in the sub-package sharding/client
• Add the collator and proposer specific methods in sharding/collator and sharding/proposer respectively.
• Write tests for the general client, to ensure that it is running correctly

More documentation can be found here :
https://docs.google.com/document/d/1__74pTWFpzfLLJ8017XeWQWJfs89YgTGxuefjkFUAaY/edit

[rauljordan]

Not a big fan of creating individual packages, especially as this will be really difficult for upstream merging. Just created #83 as an alternative proposal to this problem.

[prestonvanloon]

@rauljordan Individual packages under the sharding package make no difference on the ease or difficulty of merging upstream.

[terencechain]

@prestonvanloon I agree there's no difference, the question is do we need it. When we introduce more actors (ex: executor), are we going to create a executor package as well?

[prestonvanloon]

@terenc3t Yes, we need packages for proper code organization. As the sharding features grow, it will be unmaintainable to have a single package that does everything.

Absolutely, the execution would go in another package since it’s another responsibility.

[rauljordan]

Referenced by #85 and it includes @nisdas's work. We can close this one.