Function concept_urn 

pub fn concept_urn(name: &str) -> String

The concept URN urn:mif:<uuid> for name.

let urn = mif_core::concept_urn("source:topic:paper");
assert!(mif_core::is_concept_urn(&urn));
assert_eq!(urn, mif_core::concept_urn("source:topic:paper"));