Adjust command flags & support setup folder

[fleveillee]

The following flag configuration should be final.

shopify theme component dev

Flags
--setup-files     boolean   default: true
--watch           boolean   default: true
--theme-path      string    default: archetype-themes/explorer@latest
--locales-path    string    default: archetype-themes/locales@latest

• The dev command becomes the central command
  • The watch flag should be removed from the install command
  • The dev command should add a watcher for changes on theme files if they are local
  • The dev command should give a warning that changes cannot be watched on a theme repository if a URL was provided
  • setup files need to be handled by default; the flag should enable you to negate that option (however, the functionality will be implemented later in another ticket)