* Merge branch 'master' of C:\Projects\PHPOffice\PHPSpreadsheet\develop with conflicts.
* More trend function unit tests
* Yet more trend function unit tests
* Merge branch 'master' of C:\Projects\PHPOffice\PHPSpreadsheet\develop with conflicts.
* More statistical tests
* Further statistical tests
* Unit tests for some of the trend functions
* resolve scrutiniser objections
* Fix order of @return types :-(