Update real-fvr branch

~NOTE~

~Still WIP as we are finalizing thorough testing on our side, but~ I'd appreciate your eyes going through the code in the meantime, to see if anything jumps up just by looking. ~I will update this PR when testing on our side is finished before merging. So please don't merge until then as we don't want this in production just yet.~ 😄

List of changes

• updated with master
  • brings it one step closer to start contributing functionalities to bepro-js
• made a few tweaks to the watch and build steps to help with using a hot-localhost copy in our projects
• committed yarn.lock for consistency across environments
• removed hard lock on node minor version
  • any v14 (LTS) node should be ok to use as minor versions don't (or shouldn't) include breaking changes
• gas prices estimated from web3
  • implemented gasFactor, gasAmount, gasPrice parameters applied to transactions
  • __sendTx() now expects a second argument to override these values, hopefully I didn't add any compatibility issues with this
• left both ERC721Contract and ERC721Standard - didn't want to mess with existing code that might depend with one or the other specifically, couldn't tell which was supposed to be "the one" overall
• updated babel and eslint
  • eslint is still not perfect as I couldn't get my IDE to work with it, but should provide cleaner code pre-commit as usual
  • also follows updated standards
• when initializing contracts, only start web3Connection if needed, but ensure it's started
• I didn't run any tests as I don't have an eth network setup locally, probably broke a few?
• Allow passing opt.provider to Web3Connection, with assumed connection logic (no need for internal start() or login())
  • this allows us to leverage bepro-js through web3 wallets other than metamask
  • a next step would be to implement specific wallet logic directly into bepro-js, as it already does for Metamask, but one step at a time 😄