treewide: improve template expansion

also: support *.toml as extra configuration dictionaries

j2cfg/j2cfg-dump-yml.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+
+import os.path
+import sys
+
+
+def main():
+    sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+    import j2cfg
+
+    j = j2cfg.J2cfg(dump_only=True)
+    print(j.dump_config_yml())
+
+    sys.exit(0)
+
+
+if __name__ == "__main__":
+    main()