City Graph mapping query quality

[namedgraph]

CSV to RDF mapping queries in City Graph app are pretty poor:

• values do not match domain (e.g. schema:serviceOperator with string values)
• literals do not have datatypes (e.g. schema:maximumAttendeeCapacity values)
• properties misused, e,g, schema:maximumAttendeeCapacity used both as venue capacity (correct) and electric vehicle charger capacity (incorrect)
• schema.org namespace should change from http://schema.org to https://schema.org