patternProperties validation is not aligned with JSON-schema

[peter-plochan]

Even the OpenAPI 3 doesn't support pattern properties in schemas yet, the validator includes validation of patternProperties field within the schema. I would expect that these patternProperties should be the same as defined in JSON-schema.
The problem is that the validator accepts something like this (see implementation in schema.go):

Pet:
  type: object
  patternProperties: '^somePattern$'
  additionalProperties:
    $ref: '#/components/schemas/PatternPropertySchema'

[fenollp]

Indeed patternProperties field support should be deleted. I'll review any PR you send my way :)

[peter-plochan]

@fenollp #192 - not sure if it's enough for complete removal, but hopefully it is :)