Argument naming, ordering and logic consistency

[gouline]

Big refactor of CLI/programmatic entry point arguments, to achieve some readability and consistency.

• Arguments only belonging to dbt or Metabase are clearly prefixed with dbt_ or metabase_ respectively (common arguments are not prefixed)
• Prefix mb_ becomes metabase_ for clarity
• Optional boolean arguments should be false by default, e.g. if we mandate HTTPS to be the default (as we should because it's 2021), optional override should be use_http, instead of use_https that's true by default overridable to false
• Starting to use the new default format for header comments in VS Code, not going to replace all existing ones (too lazy, maybe in the future), but any new ones or significantly reworked ones are easier to re-create than edit, e.g. see export()

We're making a lot of breaking changes with the next release that will feature manifest parsing, we may as well break anything else we need in the process to go along with it.

(Addresses #30 among other things)

[gouline]

FYI: @z3z1ma, @fernandobrito, @remigabillet, @erika-e

[erika-e]

Should the version number change, since these are breaking changes? Otherwise looks good to me!

[gouline]

Version changes are done outside of feature PRs. The next version will include quite a few changes.