v0.7.0: Output imports and collect additional properties

New features

• Output imports/use statements for Rust and Kotlin
• Collect additional/optional properties (Rust and Kotlin/Jackson)
• Various improvements to the web UI
• Various changes to better support use of json_typegen_shared as a library

Fixes

• Kotlin:
  • Don't output empty data classes for empty objects
  • Only restrict use of hard keywords (use less rename annotations)
  • Output Any? instead of Any to include null for values of unknown type
  • Use correct Kotlin type alias syntax

Breaking changes

• Option parsing is now an optional feature.
  This is a breaking change for anyone using default-features = false and option parsing.
  Enable by adding "option-parsing" to the list of enabled features.
• Some Kotlin fields that would previously be renamed because
  they are soft keywords are no longer renamed.