Add BG delta value to HUD or Glucose chart

[bjornoleh]

It would be nice having the BG delta value easily available within FreeAPS-Loop. The alternative is to calculate this manually from the previous value after scrolling back and forth, or switch to another app. That is not efficient.

Since the BG graph autoscale, the delta value is not easily estimated from the graph.

There is some space in the line with the Glucose chart heading ("Glucose"), and possibly also in the BG cell in the HUD.

Here is a mock-up with delta displayed on the Glucose chart heading ("Blodsukker +0,1"). This would need some adjustment of font size etc.

Mock-up of delta (in red for illustration only) below BG-value, with timestamp moved slightly downwards. All time stamps should be moved down the same mount to keep it pretty (basal, insulin, battery / pod)

[bjornoleh]

For reference, this is what it looks like in FreeAPS X on an SE gen1 2016