Batch Addition and Deletion of policy rules.

[Divy Patel]

As casbin-core batch atomic transactions for addition and deletion, so leverage the features of the adapter, we should add addPolicies() and RemovePolicies methods to the adapter.

[Yang Luo]

@nodece

[Zixuan Liu]

Sorry, I don't have time to working on the issue :)

Could anyone working on the issue ?

[Divy Patel]

Okay, then I can work on this issue.