Do not override plotIt options

• The default y-axis-format can be set in the general configuration section of the yml file, but having this entry in analysisutils.plotit_plotdefaults prevents the user from changing it, short of manualy setting the option for every plot declared.

• I'd rather not change the default plotIt options for the y-axis title and for sorting according to yields. But perhaps we should have a better way of setting default options, instead of that hardcoded dict in analysisutils...