Make battery level percentage string translatable (also, default to ISO-31 percentage sign standard)
This allows for local translation teams to change the presentation format of the battery level percentage string accounting for local guidelines and standards for displaying percentage values.
See https://en.wikipedia.org/wiki/Percent_sign#Correct_style for more information.
This also changes the default from the "English" style to the ISO-31-0 standard.
Fixes #2637 (closed)