Minor Changes to FILTER Function

[oleibman]

Its first parameter is typed as array. Like all Excel spreadsheet functions, it should be mixed to avoid TypeErrors. If an argument other than an array is supplied, Excel will return VALUE, and now PhpSpreadsheet will do so as well. This had not been unit-tested. In fact, all the unit tests take place outside of spreadsheet context. New tests in spreadsheet context are added.

This is:

• a bugfix
• a new feature
• refactoring
• additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change and a link to the pull request if applicable
• Documentation is updated as necessary

[oleibman]

Scrutinizer "new issue" is the usual "unable to parse modern Phpdoc declaration". It is now suppressed.