SourceSpec v2 documentation

[claudiodsf]

This issue is to keep track of the modifications and new features which need to be documented before releasing SourceSpec v2.

• New API:
  • update the Sphinx docs to point to the new functions
  • API examples
• New CLI
  • New program names
  • New options
• Source priority when reading events (see V2 asdf #56)
• ASDF file support for traces, inventory, events (see V2 asdf #56)