Add option to ignore leakages in app calculation

[raphaeltimbo]

For now these options are disabled:

• Implement seal gas check box Implement seal gas checkbox #56

To implement the leakage check box #58

• Make the class PointFirstSection create a point when leakage values are None
• Implement leakage check box

[raphaeltimbo]

The approach of "Make the class PointFirstSection create a point when leakage values are None" seems to be too complicated.
Maybe we should just pass 0 values for balance line flow, div wall and seal leakages directly inside the app when the user choose to not calculate seal leakages.