feat(issue-221): empty failedTemplateValidator

[ivankatliarchuk]

proposal #221 and #218

Catch any errror message with failedTemplate: {}

first iteration

suite: Test empty template
templates:
  - validation.yaml
tests:
  - it: should fail when No failed document
    asserts:
    - failedTemplate: {}  // new capability. empty failed template
    - failedTemplate:
            errorMessage: "Please provide someRequiredValue"

  - it: should not fail when value is provided
    set:
      someRequiredValue: "foobar"
    asserts:
    - notFailedTemplate: {}

added parametrised tests to simplify adding more variations