Add sample for ClearContainer = false property of FragmentScreen

[phansier]

It seems to be useful having the example for overriding clearContainer property of FragmentScreen.
I've found it useful for keeping background fragment when opening new semitransparent.

If you had another idea while adding it - please let us know

[terrakok]

Hi! It's good idea! Could you share screenshot of new screen?

[phansier]

New button

And the screen itself

[terrakok]

Cool! Please, add text and button to this screen. Something like: "This is not dialog. This is regular screen." And button with text "back"

[phansier]

Done