FIRST TIME UI SETTINGS
		SetUiToApplicationStartDefault();

		-> SELECT FILES OR DROP FILES
				-> ADDING FILES IN PROGRESS UI	->AddItemToList()
													SetUiForOperationInProgress(CanelOperationCallerEnum.Import);

						->CANCEL OPERATION UI
									 SetUiForCancelOperation(CanelOperationCaller.Import);

				-> DONE
				backgroundWorkerAddItemsToList_RunWorkerCompleted()
						SetUiBasedOnItemsInList()
						{
							*
							->ONE FILE 			-> ...
							->TWO OR MORE FILES	-> ...
							->EMPTY				-> SetUiToApplicationStartDefault();
						}

->btnRemoveFromList_Click
		SetUiBasedOnItemsInList()
				{
					*
					->ONE FILE 			-> ...
					->TWO OR MORE FILES	-> ...
					->EMPTY				-> SetUiToApplicationStartDefault();
				}

->btnClear_Click
		SetUiToApplicationStartDefault();

->btnCombinePDFs_Click
	SetUiForOperationInProgress(CanelOperationCallerEnum.Combine);

	->CANCEL OPERATION UI
				 SetUiForCancelOperation(CanelOperationCaller.Import);
	->DONE
				SetUiToApplicationStartDefault();