feat: adding ability to import and display armies

When pressing the import buttons for either army the systems file explorer is opened. From there, the user can only select a csv file. If the file handler succeeds reading the army from the file, it will display the information on the scene. It displays a summary of the army with its name, a list of all units in the army and the file path where the army was imported from. A new file View has been added. It was added to simulate MVC structure. The view takes now care of the file chooser and displays information on the scene. The controller recieves action events from the fxml file.