Real-time prediction

[konakion]

Description

If one sensor doesn't deliver data, a message pops up and at certain times, you cannot stop the prediction.

Besides the prediction doesn't show any results (which model?) and there is a message saying that you have to measure an activity(!?)

[lucasliebe]

i think this works into #190 to update these toasts is already planned

maybe it's worth to consider cancelling the prediction if 3 times not enough data was collected to prevent it from getting in a loop