[FEATURE] Glossary / Documentation, clarify built-in/user defined/atomic/compound value types

[rhazn]

User Story

1. As a {user/persona}
2. I want {to have a clear glossary for value types}
3. So that {I can talk about them with others}

User Acceptance Criteria

• [ ] Single-attribute value types are referred to as atomic value types in docs and code
• [ ] Multi-attribute value types are referred to as compound value types in docs and code
• [ ] built-in value types are described as any value type that is not implemented in Jayvee code but provided by the interpreter (in docs and code)
• [ ] user-defined value types are described as any value type that is implemented in Jayvee code, including the sdtLib (in docs and code)
• [ ] A matrix of example value types is added to the docs, with two axes: Atomic/Compound and Built-in/User-defined. Examples are:
  • Atomic/Built-in: integer, text
  • Atomic/User-defined: Percent
  • Compound/Build-in: -
  • Compound/User-defined: -

Definitions of Done

• [ ] A PR has been opened and accepted
• [ ] All user acceptance criteria are met
• [ ] All tests are passing