Move the default network setting outside of built bundles - Closes #491

[faival]

What was the problem?

A flag is used at build time to set testNet or mainNet as the preferred network to show, this should be changed to be set clientside

How did I fix it?

• replace npm scripts goals used by webpack build approach
• replace usage of env variables in app codebase
• provide a way to copy built assets and only replace a flag in main html

How to test it?

• run the following steps:

npm install
npm run build
npm run build:testnet

• then open the generated app built in ./app/build/index.html
  (assert when passing ?showNetwork=true) points to mainnet
• then open the generated app build in ./app/build-testnet/index.html
  (assert when passing ?showNetwork=true) points to testnet

assert for both builds that wen actively setting a value on local storage of browser with:

localStorage.setItem('defaultNetwork', 'mainnet' || 'testnet' || 'customNode'), 

then that value is used next time the application is reloaded.

Review checklist

• The PR solves Move the default network setting outside of built bundles #491
• All new code is covered with unit tests
• All new features are covered with e2e tests
• All new code follows best practices

[slaweet]

I would add another comment to explain that //defaultNetwork is used npm run build:testnet. Otherwise, seeing just this file makes it look like a useless comment that I would delete if I didn't know the context.

[faival]

updated

[slaweet]

The if could also check if default network is already defined in local storage. And don't set it in that case. That way, we can set defaultNetwork on localhost when developing (when needed) and it won't be overridden on each page reload.

[faival]

done

[slaweet]

Thank you, Pablo