Upgrade from OpenAPI 3.0 to 3.1

[cookeac]

Update to OpenAPI 3.1

The following changes have been made to all OpenAPI files in the url-schemes folder:

• Updated to "openapi": "3.1.0"
• Updated to version 1.4 (ahead of the ADE 1.4 release)
• Updated all tags to ADE-1.4-xxxx

The following changes have been made to JSON Schema files in the types and resources folders where "nullable": true was previously specified:

• replace "type": "string" with "type": ["string", "null"]
• replace "type": "number" with "type": ["number", "null"]
• replace "type": "integer" with "type": ["integer", "null"]
• replace "type": "boolean" with "type": ["boolean", "null"]
• replace "type": "array" with "type": ["array", "null"]

Where a complex type (imported with "$ref" was previously nullable):

• If the type was an object, add "type": ["object", "null"] before the $ref
• If the type was a string (an enumeration or an icarDateTimeType), add "type": ["string", "null"] before the $ref

Resolves #239