API: changed date-format, camelCase instead of snake_case, null values, update and create for customer and project (#718)

README.md

@@ -22,7 +22,7 @@ Kimai is a [multi-language application](https://www.kimai.org/documentation/tran
 
 ### Requirements
 
-- PHP 7.1.3 or higher (test your system compatibility with the [requirements-checker](http://symfony.com/doc/current/reference/requirements.html))
+- PHP 7.2 or higher (test your system compatibility with the [requirements-checker](http://symfony.com/doc/current/reference/requirements.html))
 - The PHP extensions [xml](http://php.net/manual/en/book.xml.php), [mbstring](http://php.net/manual/en/book.mbstring.php), [gd](http://php.net/manual/en/book.image.php), [intl](https://php.net/manual/en/book.intl.php), [zip](https://php.net/manual/en/book.zip.php) and [PDO](https://php.net/manual/en/book.pdo.php) with either [pdo_sqlite](https://php.net/manual/en/ref.pdo-sqlite.php) or [pdo_mysql](https://php.net/manual/en/ref.pdo-mysql.php) enabled
 - If you use MariaDB, make sure its at least v10.2.7 (see [FAQ](https://www.kimai.org/documentation/faq.html))
 - A modern browser, Kimai v2 might be broken on old browsers like IE 10