Add unit test with Pester

[NicolasBn]

Use pester to add unit tests to cover this :

• NodeUtility Class : ParseFile() IfNode without children
• NodeUtility Class : ParseFile() IfNode with children
• NodeUtility Class : ParseFile() ForeachNode without children
• NodeUtility Class : ParseFile() ForeachNode with children
• NodeUtility Class : ParseFile() WhileNode without children
• NodeUtility Class : ParseFile() WhileNode with children
• NodeUtility Class : ParseFile() SwitchNode without children
• NodeUtility Class : ParseFile() SwitchNode with children
• NodeUtility Class : ParseFile() ForNode without children
• NodeUtility Class : ParseFile() ForNode with children
• NodeUtility Class : ParseFile() DoUntilNode without children
• NodeUtility Class : ParseFile() DoUntilNode with children
• NodeUtility Class : ParseFile() DoWhileNode without children
• NodeUtility Class : ParseFile() DoWhileNode with children