* Merge branch 'master' of C:\Projects\PHPOffice\PHPSpreadsheet\develop with conflicts.
* New statistical tests
* Sniffs
* Additional statistical function unit tests
* Additional statistical function unit tests
* Fix case-sensitivity
* Fix HARMEAN code logic
* Unit tests refactored into individual files for all logical functions
Implemented IFNA()
* Fix silly typo
* NOT needs ...args to allow for test when no argument passed
* Codestyle
* Use instance asserts
Mark Baker