Feature: better display

[kpp39]

I modify Display.cpp for:

1. fixed the bug, when you open status page and press tare or sleep, message overlap with status page and make mess.
2. when it's negative value or over 99 grams, decimals not shown
3. when timer exceeds 60 seconds, it switch from ss.sT to m:ss format. I think 60 secs is sufficient to remember where timer is so i drop "T" label 🤣