SHAPE UP: support for ENS domains

[andregoncalves]

Shape up here: https://confluence.kyc-chain.com/display/SEL/Support+for+ENS+domains https://ens.domains/

1- register the sk .eth name (selfkey.eth?) 2- change wallet code to be able to resolve ens names when inputing addresses (and DIDs?) 3- (optional) have a new feature where by users can register their selfkey.eth subdomain andre.selfkey.eth

Prior-art: https://confluence.kyc-chain.com/display/RND/key.eth+ENS+Resolution