Triage finschia-sdk#143

[0Tech]

The subject of the triage:

• feat: signature verification cache (#41) finschia-sdk#143

[170210]

This PR can be abandoned.
Cosmos is solving this problem(wait for merge), and is superior to our method.

• [Feature]: add SignatureCache for checkTx and DeliverTx cosmos/cosmos-sdk#15780
• feat: cache for signature verification cosmos/cosmos-sdk#18422

[0Tech]

Conclusion:
We need to make the cache size configurable. Other than that, it would be OK to close this.