implement 'gaiacli init' / client init commands

[alexjipark]

if I run 'basecli init' with any option, an error saying "ERROR: TODO: Command not yet implemented" occurs.

Do you have any idea to solve this problem?

[zramsay]

it hasn't been implemented yet. i've re-named the issue. stay tuned

[ebuchman]

This needs to do things like persist the chainid and node URL and the initial validator set (which shoudl be authenticated socially).

See how we use to do it here for reference: https://github.com/cosmos/cosmos-sdk/blob/bucky/reference-v0.8.0/client/commands/init.go

[ebuchman]

Replaced by #1275 (comment)