Improve compatibility with dark color schemes

Changes:
1) css files compatible with themes are generated in ~/.config/kmymoney/
each time at startup,
2) redundant colors were removed from options and are always fetched
from color scheme,
3) fixed colors and letter cases in css files for css adaptability,
4) KMyMoneyGlobalSettings::schemeColor is for all color requests,
5) Use AppDataLocation instead of deprecated DataLocation.

BUG:369529
FIXED-IN:5.0
Signed-off-by: Łukasz Wojniłowicz <lukasz.wojnilowicz@gmail.com>