[CAT-971] Web View for Password Forgotten in Upload Dialog 

When you are not logged in and press the button “Upload” a Dialog appears where you can press “Password Forgotten” which will lead you to your installed Browser.

In this pull request, I changed the code to open a WebView instead, like when you press on “Help” or “Explore” in the Main menu.

This PR is same as https://github.com/Catrobat/Catroid/pull/966