[Elephant] Issue #189 Added SignSchema

[rg911]

• Introduced the SignSchema to make KeyPair generation consistent between Catapult and NIS.
• SignSchema contain 2 enum value: KECCAK_REVERSED_KEY and SHA3. The SDK by default uses SHA3 which is the Catapult signature schema.

Concept

Since Catapult server is using 'SHA3' as default hasher while NIS1 (current public net) is Keccak based. This change will allow Catapult SDK to be compatible to NIS1's hashes e.g. KeyPair, Address, Encryption, Decryption etc..

By default, the SDK uses SignSchema.SHA3 for hashing unless explicitly specified KECCAK_REVERSED_KEY.

• Affected classes:

1. KeyPair
   • createKeyPairFromPrivateKeyString
   • sign
   • verify
   • deriveSharedKey
2. Crypto
   • encode
   • decode
3. Account
4. Address
   • createFromPublicKey
5. PublicAccount
   • createFromPublicKey
   • verifySignature
6. All transaction signings

[coveralls]

Pull Request Test Coverage Report for Build 554

• 127 of 131 (96.95%) changed or added relevant lines in 18 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.4%) to 60.677%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/core/crypto/KeyPair.ts	17	18	94.44%
src/infrastructure/builders/AggregateTransaction.ts	3	4	75.0%
src/core/crypto/nacl_catapult.ts	38	40	95.0%

Totals
Change from base Build 549:	0.4%
Covered Lines:	5900
Relevant Lines:	8405

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💛 - Coveralls