Feature: Fetch metadata Browser-Harmony

[RolandoAndrade]

Why is this change neccesary?
Because is neccesary retrieve the ERC721 contract metadata from the browser.

How does it address the issue?
I created an interface for contract manipulation at contacts/domain where I defined the ERC721Contract with the method getMetadata(), in the future here will be defined all the methods that we will use, the idea is manipulate the contracts in an abstract way, so we can use the same procedures at front applying polimorfism.

The implementation of the abstract contract is ERC721HarmonyContract located at contracts/infrastructure, here I put all the Harmony logic and contract wrappers. I created an instance of it as example at index.js. If we use polimorfism, we could instance an ERC721EthereumContractwithout change anything in the code, only the line where it is instanced.

What side effects does this change have?
There are a lot of changes in dependencies that must be installed. I deleted the dist file generated by webpack build process because it changes frecuently and could create git conflicts. On the other hand, I added typescript, but my configuration allows Javascript, so the only side effect that could be appear is a conflict in build, and if you delete the dist file it won't appear.

[jcstr]

Thanks @RolandoAndrade for this! I'll merge because we need it for the whole project.