If the auto-generated BlockchainRESTClient works, deprecate the hand-rolled one; if it doesn't, remove it

[gthoma17]

If the auto-generated client works, make sure you also replace the hand-rolled types used by the REST client (ie BlockchainAccountModule)

[gthoma17]

Update to: deprecate the autogenerated client

[gthoma17]

Demo: https://github.com/diem/explorer/pull/111/files