fix faucet drip amount and symbol display

[brenzi]

The drip amount is hardcoded to mKSM and thousand-separator is a comma, which is misleading in german.

On Gesell, GesellPioneerPot faucet has 1 ERT drip amount

shown as 1,000 mKSM
should be 1.00 ERT

I suggest to stay with 3 significant digits and apply [SI prefixes] with the . as decimal separator (https://mathworld.wolfram.com/SIPrefixes.html)