Improvements

[gmchad]

Improves the readability and functionality of the examples codebase.

• circuit download script
• .env file for persistent environment variables
• move init boilerplate code to walletSetup.ts
• encapsulate redundant code in functions in index.ts
• add cli to enable running one example at a time

[gmchad]

hey @vmidyllic could we get this merged in? This should simplify the examples for new users.

[nedgar]

+1. These are some nice consumability enhancements. One issue: dotenv should be a runtime dependency, not dev.