First task to introduce ATH Tests for the folder plugin.

Jenkins Version: 1.625.2
Plugin Version: 5.1

Use Case: Folder Creation.
Scenario:

1. Create a folder.
2. Check the folder exists with the provided name and that the user can enter it.

The goal of this task is also using this simple scenario to start introducing Folder support in the ATH. As part this effort, this task include:

• As folder are non-buildable jobs, create a TopLevelItem abstraction used by both jobs and folders.
• Review object equality criteria for items, as the presence of a hierarchy enables the existence of items with the same name in different folders.