Refactor irishub sdk

[chengwenxi]

Summary

Now, irishub-sdk contains all modules in one repo, we plan to split them into core-sdk and multiple repos(for each module), so that users can assemble them without add all modules.

Implementing

• go-sdk

[Nicke-lucky]

core-sdk
The Core-SDK contains the following core functions

Auth module;

Bank module;

Keys module;

Keys requires an interface designed to support SM2 (for the federation chain IRITA)
At present, Keys is mainly the entrance, and the actual logic is in Crypto

base_client. go

[zhangyelong]

Closing in favor of irisnet/core-sdk-go#10