changed slider setting for coal price rises in the SER 2020 and SER 2023 preset scenarios. Relates to issue #832.
Updated SER 2020 and SER 2023 carrier and co2 prices after discussion with Berenschot's Niki Lintmeijer on what source to use. Decided to use different source.
Merge pull request #833 from quintel/correct_coal_price_ser

Correct fuel price slider setting for SER preset scenarios