Add PHP 7.4 support (#464)

* Add PHP 7.4 to build matrix

* DB fix

* YAML parser fix in test data

* Show versions

* Package updates

* Track used ICAOs

* 7.4 METAR parsing fix

* METAR parser fix

* Formatting

* Add meters to response units

* Call instance for unit conversion

* Return value

* Catch exception for unknown quantity

* Comment fix

* Formatting

* METAR parsing fixes on PHP 7.4

* Package updates

* More random airport ID

* More random airport ID

* Properly disable toolbar

* Semver written out to version file

* Use dev as default identifier

tests/MetarTest.php

@@ -112,7 +112,7 @@ class MetarTest extends TestCase
         $this->assertEquals(1000, $parsed['clouds'][0]['height']['ft']);
         $this->assertEquals(1600, $parsed['clouds'][1]['height']['ft']);
         $this->assertEquals(4000, $parsed['clouds'][2]['height']['ft']);
-        $this->assertNull($parsed['clouds'][3]['height']['ft']);
+        $this->assertNull($parsed['clouds'][3]['height']);
     }
 
     public function testMetar3()