Add build in PHP syntax check on files.

Before certain things could still pass unless they were explicitly
looked for, but PHP checks basic syntax to make sure the file is even
readable.
Merge branch 'feature/php_syntax' of https://github.com/blainesch/PHP_CodeSniffer
Changelog + a few changes to make sniff consistent with others
Merge branch 'master' into phpcs-fixer

Conflicts:
	package.xml