Add swagger model entry that accepts raw openapi schema text as yaml or json

[kulgan]

Tentative strategy will be to have this model class parse the provided text and generate the proper model class representing the text.

@swagger.RAW(
    yaml="""
   get:
      tags:
        - developers
      summary: searches inventory
      operationId: searchInventory
      description: |
        By passing in the appropriate options, you can search for
        available inventory in the system
      parameters:
        - in: query
          name: searchString
          description: pass an optional search string for looking up inventory
          required: false
          schema:
            type: string
        - in: query
          name: skip
          description: number of records to skip for pagination
          schema:
            type: integer
            format: int32
            minimum: 0
        - in: query
          name: limit
          description: maximum number of records to return
          schema:
            type: integer
            format: int32
            minimum: 0
            maximum: 50
      responses:
        '200':
          description: search results matching criteria
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/InventoryItem'
        '400':
          description: bad input parameter"""
)
def route():
   pass

This should generate a swagger.GET instance. Research possibility of pulling this also from docstrings