Design properties: project, author and licence in the design, its exports and inspect_design (#1015) (#1189)

A design carries metadata (format 21): project, part number, revision, author, organization, description and license, plus other tools' data under reverse-DNS keys, kept as written. Edited in the Design Properties window (Document Settings), set by document.metadata.set, reported by inspect_design, and written into STEP, IGES and 3MF where the format has a place for them. Translated, with tests.

crates/engine/src/cmd/mod.rs

@@ -43,6 +43,7 @@ mod material_properties;
 mod materials;
 mod measure_sel;
 mod mesh;
+mod metadata;
 pub(crate) mod motion;
 mod parts;
 mod script;
@@ -252,6 +253,7 @@ pub fn command_specs() -> Vec<&'static CommandSpec> {
     v.extend(script::COMMANDS.iter());
     v.extend(parameters::COMMANDS.iter());
     v.extend(file::COMMANDS.iter());
+    v.extend(metadata::COMMANDS.iter());
     v.extend(inspect::COMMANDS.iter());
     v.extend(materials::COMMANDS.iter());
     v.extend(material_properties::COMMANDS.iter());