Export and Import from a single YAML file

@Fryguy @gmcculloug @chessbyte @tinaafitz 
For export and import of automate models we have 3 ways to store the data based on YAML. We currently have (1) ZIP file that can store all the YAML's or (2) store all the YAML's in a directory. This PR adds a 3rd one which is to have all the model into a single consolidated YAML. The single consolidated YAML helps us with our specs where we don't have to store all the model YAML files separately in a directory.
Aren't these two methods pratically identical?  Could this be simplified to...

```ruby
  def get_filenames(parent_path, file_name)
    paths = get_filenames_with_proc(parent_path) do |key, hash|
      hash.has_key_path?(*[key, file_name])
    end
    paths.sort.collect { |path| "#{path}/#{file_name}" }
  end

  def get_filenames_with_proc(parent_path)
    path_list = parent_path.split('/')
    return [] unless @yaml_model.has_key_path?(*path_list)

    hash = @yaml_model.fetch_path(*path_list)
    selected_keys = hash.keys.select do |key|
      yield(key, hash)
    end
    selected_keys.sort.collect { |key| "#{parent_path}/#{key}" }
  end
```