MTS-S template: Application bar Expander in Mainview.xaml does not collapse[BUG]

[Krisztian Olah]

closes #99
Describe the bug
Pressing the collapse button changes the button state, but not the content state to collapsed.

To Reproduce
Steps to reproduce the behavior:

1. Go to main view screen.
2. Click on the collapse button in the bottom rigth corner.
3. See no effect on the content on the small arrow.

Expected behavior
It's expected that the bar collapses to its minimum size and does not display its contents.

Screenshots

[peterbarancek]

closes #99