adjustments as discussed today
Merge pull request #45 from jdammers/preproc_unfiltered

- add keyword ‚notch_filter’ if ICA cleaning is applied to unfiltered data
- add keyword ‚unfiltered’ to apply ICA cleaning to unfiltered data
- adjustments in the filter settings if ICA cleaning is applied to unfiltered data. Now it is possible to commit an array of frequencies which should be removed.