Add setup to sell item and use generic types

[joshuahannan]

Closes #104
Closes #95

• Adds setup storefront logic to sell item transactions so that they don't have to run a separate setup transaction
• Use generic token types in the V2 transactions so developers don't have to replace with their own specific types
• Update some import placeholders

[sisyphusSmiling]

Looks good! Made a couple minor suggestions for consistent camel case - there are a couple places where pascal case is used.