Returns a number that is internally used by wem to identify concept.
Returns Unknown if the parameter is unknown.
ConceptId(concept)
ConceptId('tickets')
=>Result: 382446
ConceptId(unknownconcept)
=>Result: unknown
ConceptId(
first(concept of [1482498: Colors]
where concept:'SecondaryColor' = true)
)
=>Result: 113787
