Bring back smooth scrolling

[oparoz]

First attempt at fixing #500.

The improvements range from not visible to astonishing on the devices I've tested. The devices which benefit the most seem to be iOS based.

This introduces the changes that @fuhaoshih tried to introduce with #285, but without the side effects (at least in the scrolling).

The best quick test you can do is scroll through a list of files on the Files side and then switch to Gallery and scroll again.

The standard and public templates should be combined in a future PR as they're very similar now.

Platforms

Desktop

• Chromium/win10: no visible change
• Firefox/win10: no visible change
• Edge/win10: no visible change
• IE11/win10: no visible change

Mobile

• Chrome/ios9: huge performance gains. Activates smooth kinetic scrolling
• Safari/ios9: huge performance gains. Activates smooth kinetic scrolling with bouncing edges
• Browser/BB10: improves scrolling performance
• Chrome/Android 4.x: huge performance gains. Activates smooth kinetic scrolling
• Firefox/Android 4.x: no visible change. Seems like hardware acceleration is not available on 4.x
• Chrome/Android 5.x
• Firefox/Android 5.x
• Chrome/Android 6.x
• Firefox/Android 6.x

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@jancborchardt @Henni @setnes @deMattin @mmattel @Spacefish @Bugsbane @MorrisJobke @jospoortvliet

[oparoz]

I've performed some tests to make sure it wouldn't block any future template extension and we will have to write our own CSS in order to be able to keep a smooth photowall or wait for core to fix their templates before trying to add a navigation panel.