Remove packages collection and fix most pages

[aldeed]

Resolves #13
Resolves #10
Resolves #80
Impact: breaking
Type: feature

Changes

Lots of changes, all related to either removing all use of the Packages collection or getting admin pages working properly again.

• Remove UI for updating and validating SMTP email settings because the API no longer uses them.
• Fix image uploading and display
• Move "System Information" (plugin versions) UI to its own Settings page and load it from GraphQL
• Fix the Payment settings page by removing most of it and loading the payment service enable/disable UI using GraphQL. The example payment settings form was only for an example and wasn't used anywhere, and the Stripe payment settings form was only for the API key, which is now set in an environment variable on the API service.
• Fixed errors on the Accounts page so it displays and works again. Updated to hard-code the list of auth roles for now because the Packages collection is gone.
• Fix the shipping settings page and update the Shipping Rates table and form to use GraphQL data.
• Move discount codes UI to its own Discounts page instead of being on the payment settings page.
• Fix the address validation rules table and form by updating it to use GraphQL data
• Remove a bunch of unused code and files

Breaking changes

Only in that everything here is assuming 3.0 API, and the Packages collection is no longer updated or used.

Testing

NOTE: Recommend testing with this API branch, or some translations will be missing: reactioncommerce/reaction#5977

General testing of all areas of the UI that were touched. Specifically shipping settings, payment settings, discounts, accounts, address validation.

Verify uploading images now works.

[willopez]

Tested UI, looks good and code looks good too.