Adds Scenario Schema + Schema Validation logic

[Korving-F]

This addition adds a specification of a Scenario description file and code to validate adherence, Example:

from cerberus import Validator
import yaml

schema = {'name': {'type': 'string'}}
v = Validator(schema)

with open('scenario_file.yaml', 'r') as f:
    data = yaml.safe_load(f)

if v.validate(self.scenario_path):
    print("Scenario is valid according to schema")
else:
    print(f'The scenario failed validation: {v.errors}')