Custom TransactionSigner and eth-account module improvements.

[nivida]

Description

This PR fixes #2356 #2378 #1998 #1255 #2300 and will also improve the QA of the module.

Web3 Accounts Refactoring

The eth-accounts module is one of the last modules which didn't got improved during the last refactoring of the core modules.
My idea now is to clean up the eth-accounts module and to add a transactionSigner options property for the eth module.

This sounds like a big refactoring but I will mostly just move the things.

TransactionSigner

It will be possible to create your own class of type TransactionSigner and inject it over the options property. The class name TransactionSigner is a reserved class name and will be used for the internal signer class.

interface TransactionSigner {
  sign(txObject: Transaction): Promise<SignedTransaction>
}

interface SignedTransaction {
  messageHash: string,
  v: string,
  r: string,
  s: string,
  rawTransaction: string
}

Example

const eth = new Eth(provider, {transactionSigner: new HDWalletSigner(...)});

Accounts

The interface of the Accounts class (web3.eth.accounts) will still be the same.

Type of change

• Bug fix
• Enhancement

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no warnings.
• I have updated or added types for all modules I've changed
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run test in the root folder with success and extended the tests if necessary.
• I ran npm run build in the root folder and tested it in the browser and with node.
• I ran npm run dtslint in the root folder and tested that all my types are correct
• I have tested my code on the live network.

[coveralls]

Coverage increased (+1.4%) to 94.619% when pulling 13eb73d on issue/2356 into 7f5a390 on 1.0.

[sokun-chorn-webjet]

duplicates with line 62

[nivida]

This isn't a duplication. I'm just passing the TransactionSigner dependency over the options. Check out the Eth module for seeing the real reason why I'm doing this. The complete dependency handling will get improved later (removing of the Factory objects etc.).

[csokun]

I mean this assignment this.options = options; it happens twice probably a left over from git merge.

[nivida]

Oh sorry, I got it wrong. Thanks.

[rstormsf]

@nivida Any great example on how to use it?

[sydneyitguy]

maybe forgot to remove?