Add PSR4 namespace check for classes, traits, interfaces.

[dereuromark]

Try to port not maintained https://github.com/suin/phpcs-psr4-sniff

BUT:
It doesn't quite seem to work

If I have a namespace of

Foo => src/Foo

defined, It does not report issues like

Foo\Bar\Baz => src/Foo/Baaaaa/Baz

Which it should IMO

[dereuromark]

Using getcwd() I think I was able to fix the base path handling, which then made it work for me.

[dereuromark]

One false positive issue left

	"autoload-dev": {
		"psr-4": {
			"QueueScheduler\\Test\\": "tests/",
			"Cake\\Test\\": "vendor/cakephp/cakephp/tests/",
			"TestApp\\": "tests/test_app/src/"
		}
	},

and

FILE: /work/git/cakephp-queue-scheduler/tests/test_app/src/Application.php
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FOUND 1 ERROR AFFECTING 1 LINE
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 10 | ERROR | Class name is not compliant with PSR-4 configuration. It should be `QueueScheduler\Test\test_app\src\Application` instead of `TestApp\Application`. (PhpCollective.Classes.Psr4.IncorrectClassName)
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