Vaccine walkthrough improvements

[geel9]

Overview

This PR (apologies for the size) makes the following improvements to the vaccine walkthrough (tracked from #659)

• Ecosystem creation is now explained and is the first step
  • Ecosystem creation now has a sub-step, which is setting the created ecosystem as the default ecosystem in CLI and SDKs
• Normalized / fixed template schema between Typescript and CLI
  • Other languages pending
• Credential is now issued using IssueFromTemplate, instead of using a raw pre-prepared VC JSON-LD document.
  • Only for CLI and Typescript; other languages pending
• Proof is generated for entire credential, not a subset
  • Removes need to go over JSON-LD frames in walkthrough, simplifying happy path
  • Added an infobox informing users of ability to generate selective proofs, prompting them to read more about it
  • Only for CLI and Typescript; other languages pending
• Explanatory prose added to Define a Template section
• Replit text hidden (until we actually have replits)
• Fixed incorrect CLI commands (--alias, --profile, etc. don't exist)
• Prose pass on Send Credential to Allison and Create Accounts sections
• Misc. smaller tweaks

There is still more to be done, but the PR is already quite large, so I'll push this one first.