Libre 2 + fixes

fix #126 - Enchance Calibration Warning, message adapted

fix #118 - when using mmol, alarms and colors on home screen are inconsistent for the same mmol value

if sensor active, and user swithes from master to follower, confirmation will be asked, because switching from master to follower stops the active sensor

fix #148 show battery level in NightScout

fix #152 Allow different nightscout port

don't show Nighscout API Secret and Dexcom Share password in plain text on the settings screen

removed all oop web related functionality

Libre 2