Metadata in KeY proof files

[wadoon]

As discussed in a KaKeY meeting: We introduce a new "section" in KeY files dedicated to metadata:

\metadata <json-obj>;

In contrast to \settings and \proofObligation, this section does not contain proof-relevant information.

This section is helpful for following reasons/information:

• ui data
  • last opened goal
  • undo steps
• proof statistics
• whether SMT is required

These data are filled in automatically and can be restored retrieved from a proof object.