Improve parallax on mobile devices

[ojh050118]

Describe the new feature:
Reducing the parallax delay will make your wallpapers appear to teleport in a mobile environment.
I think it is not bad to increase the parallax delay.
Proposal designs of the feature:

2019.1113.0:

Future (example):

[swoolcock]

Parallax functionality will likely be changing based on whether you have a pointing device connected. In future it shouldn't even be possible to teleport the parallax as such.

[peppy]

Mobile device parallax and cursor handling should definitely be improed, but this won't be done via reverting.

We are focused on the desktop experience first and foremost.

[bdach]

Should be improved with resolution of ppy/osu-framework#1514 to begin with, but then we might want to look into using accelerometer output for the parallax effect on mobile - but as stated above, this is a long ways away.