Summary
- prefer persistent hash code for cachable items (see also 72b13af7f266);
- merged
- more operations: record overall exported entities;
- merged
- added dummy_fof prover to Sledgehammer
- fixed malconfigured option output_dir in mirabelle
- merged
- clarified export of formal entities: name space info is always present, but content depends on option "export_theory";
- proper name space "kind": this is a formal name, not comment;
- more uniform signatures in ML and Scala;
- merged
- fixed typo
- added dummy_thf prover to Sledgehammer