Adapts checksum functionality to RSKIP60 and EIP55

[alepc253]

Description

This PR adapts checksum functionality to RSKIP-60 compatible with EIP-55.
The implementation considers sending optional chainId parameter to checksum methods (with chainId = null as default, Ethereum checksum is applied).

Benefit

• Allows checksum implementation in any network.
• Can distinguish between testnets and mainnets.

Type of change

• Bug fix
• New feature
• Breaking change
• 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 an ethereum test network.

[coveralls]

Coverage increased (+0.3%) to 95.969% when pulling 84d28d6 on alepc253:rskip-60 into 98e3a10 on ethereum:1.0.

[nivida]

Thanks for submitting this PR!

Could you update the related documentation and the types for both methods?

[alepc253]

@nivida thanks! I'm working on your reviews.
One important aspect to consider (and still didn't boarded) is the method inputAddressFormatter from web3-core-helpers/src/Formatters.js. chainId should be added to that formatter to be consistent to this change. I guess it would be very helpful to have chainId as a global parameter but I don't know if that is possible at this level... what do you think?

[nivida]

@alepc253 I would like to write that down in a new issue and to implement it later as an enhancement. The question will be if Web3 should automatically load the chainId from the connected node if no chainId got defined from the developer.