Add the possibility to define map center without default lat/lng values

Author: dkliemsch

_config/googlemapfield.yml

@@ -16,3 +16,6 @@ BetterBrief\GoogleMapField:
     default_field_values:
       Latitude: 30
       Longitude: 0
+    center:
+      Latitude: 30
+      Longitude: 0

client/js/GoogleMapField.js

@@ -14,7 +14,7 @@
 		}
 		field.data('gmapfield-inited', true);
 		var settings = JSON.parse(field.attr('data-settings')),
-			centre = new google.maps.LatLng(settings.coords[0], settings.coords[1]),
+			centre = new google.maps.LatLng(settings.center[0], settings.center[1]),
 			mapSettings = {
 				streetViewControl: false,
 				zoom: settings.map.zoom * 1,

src/GoogleMapField.php

@@ -155,6 +155,10 @@ public function Field($properties = array()) {
 				$this->recordFieldData('Latitude'),
 				$this->recordFieldData('Longitude')
 			),
+            'center' => array(
+                $this->getLatData() ?: $this->getOption('center.Latitude'),
+                $this->getLngData() ?: $this->getOption('center.Longitude'),
+            ),
 			'map' => array(
 				'zoom' => $this->recordFieldData('Zoom') ?: $this->getOption('map.zoom'),
 				'mapTypeId' => 'ROADMAP',
@@ -242,15 +246,15 @@ public function getDefaultValue($name) {
 	 */
 	public function getLatData() {
 		$fieldNames = $this->getOption('field_names');
-		return $this->data->$fieldNames['Latitude'];
+		return $this->data->{$fieldNames['Latitude']};
 	}
 
 	/**
 	 * @return string The VALUE of the Longitude field
 	 */
 	public function getLngData() {
 		$fieldNames = $this->getOption('field_names');
-		return $this->data->$fieldNames['Longitude'];
+		return $this->data->{$fieldNames['Longitude']};
 	}
 
 	/**