Task: Dependencies are exported as a JSON array

- The 'json.depends.array' setting controls whether dedendencies are encoded as
  a JSON array, or comma-separated string.
- The default value is on.
- Both forms are imported.

src/commands/CmdShow.cpp

@@ -163,6 +163,7 @@ int CmdShow::execute (std::string& output)
     " journal.time.start.annotation"
     " journal.time.stop.annotation"
     " json.array"
+    " json.depends.array"
     " list.all.projects"
     " list.all.tags"
     " locking"