Corrected p-Value for the look-elsewhere effect

- Applied Šidák correction when there are more than 2 variations in the split test
- Added tests
Fixed the number of independent experiments used for the Sidak correction

- Clarified wording
- Adjusted tests
Fixed number of independent experiments again

- Fixed typo
- Adjusted tests
Added docu
Used data provider for readability
Docu
Merge pull request #1553 from fauvel/issue-1553

Add Šidák correction to the split test significance