Show next day in the afternoon

[Antricks]

(Depends on #6 ) We should show the next day, maybe automatically switching when in monitor mode - at least in the afternoon. For that we obviously need to pre-load the next and the current day, which is already mentioned in #6

[Antricks]

We now have a cache, which should make things easier hopefully. I feel like we'll need to refactor the whole code sooner or later though to make everything more object-oriented. Having something like a day object sounds way better than manipulating around in the HTML imperatively.

[Antricks]

Now, this issue is the only one open that's for me... Before I'll start working on this, we'll need to modularize everything neatly though. I certainly don't want to mess around with some dirty spaghetti code when doing something like a split-screen or so. Maybe, RCS might also have ideas on Thursday regarding how he imagines this to look.

[Antricks]

Okay, RCS prefers a swipe between both days over a split-screen. We could maybe implement both and make it a user choice in the settings, but the focus should be on swiping then.