feat: Automate deployments through tasks!

[octalmage]

This PR includes a few features/improvements.

1. The ability to call storeCode and instantiate from inside of tasks. I've added an example to the readme which can be viewed here: https://github.com/terra-money/terrain/blob/de5627172ec60da427c7abd5ae6721fa60051087/README.md#creating-tasks
2. Moving reused flags to src/lib/flag.ts. There were situations where flags are reused, but the description or default was different depending on the command. In these situations we can move the flag to this new file, import it, and reference the same default value and description.
3. Added a default value for --signer. When using LocalTerra, we can assume the signer will be the test1 wallet. This improves usability for local development.
4. I ran the readme generator which overwrote some of the work by @terran6. If we do want to modify the oclif readme template we should do without manual tweaks to the readme, because they get reverted.
5. Small tweaks and cleanup based on eslint rules.