X files factor fixes

Rebased and cleaned version of #63

"It seems as if the method was left over after implementing a comparison using only two digits of the float values for xFilesFactor. This leads to migration of every single whisper file"
@esc just being picky, but would be nice for this comment to be where
```
# check to see if the current and configured aggregationMethods are the same
```
is and for that comment to be in the right place...  I can rebase and open a new PR if you can't be bothered ;-)