Utee api update

[SimonWan]

1. Comment and improve object API.
2. Complete, comment and improve crypto API.
3. Complete Arithmetical API.
4. Add the asymmetric cipher example for the Asymmetric operations of crypto API.
5. Add the big-int example for arithmetical API.
6. Add the Diffie Hellman, message digest, and authentication encryption example for crypto API.
7. Update all examples with proto.
8. Merged with the message branch.