!!! FEATURE: Raise phpunit to v8.1

[johannessteu]

This change raises the phpunit requirement to v8.1. This might be breaking for you as phpunit introduced return types on methods like public setUp(): void as well as public tearDown(): void. PHPUnit also deprecated a lot of methods. You might find here some more background information about replacements for your assertions.

Resolves #1506

[johannessteu]

For Unit-Tests i'm down to this:

WARNINGS!
Tests: 4845, Assertions: 9410, Warnings: 16, Skipped: 52.

Some warnings are left regarding sebastianbergmann/phpunit#3338.
But I'm actually not sure right now how to fix those. At some places we might be able to use ObjectAccess.

There were 16 warnings:

1) Neos\Flow\Tests\Unit\Http\BrowserTest::browserFollowsRedirectionIfResponseTellsSo
attributeEqualTo() is deprecated and will be removed in PHPUnit 9.
attribute() is deprecated and will be removed in PHPUnit 9.
readAttribute() is deprecated and will be removed in PHPUnit 9.
getObjectAttribute() is deprecated and will be removed in PHPUnit 9.

2) Neos\Flow\Tests\Unit\I18n\Cldr\CldrRepositoryTest::modelIsReturnedCorrectlyForSingleFile
assertAttributeContains() is deprecated and will be removed in PHPUnit 9.
readAttribute() is deprecated and will be removed in PHPUnit 9.
getObjectAttribute() is deprecated and will be removed in PHPUnit 9.

3) Neos\Flow\Tests\Unit\I18n\Cldr\CldrRepositoryTest::modelIsReturnedCorrectlyForGroupOfFiles
assertAttributeContains() is deprecated and will be removed in PHPUnit 9.
readAttribute() is deprecated and will be removed in PHPUnit 9.
getObjectAttribute() is deprecated and will be removed in PHPUnit 9.
[...]

[johannessteu]

To make travis run with phpunit 8.1 we need this one merged
neos/flow-development-distribution#38

[johannessteu]

Open tasks Unit-Tests:

• Adjust composer.json dependencies
• Refactor deprecated @expectedException annotation
• Refactor to use assertEqualsWithDelta()
• Refactor to use assertStringContainsString()
• Adjust other warnings for deprecated code
• Double check that travis is acutally running phpunit v8

Open tasks Functional-Tests:

• Adjust composer.json dependencies
• Refactor deprecated @expectedException annotation
• Refactor to use assertEqualsWithDelta()
• Refactor to use assertStringContainsString()
• Adjust other warnings for deprecated code
• Double check that travis is acutally running phpunit v8

[daniellienert]

Looks good and tests are working