Constrain crop proportions by default, with checkbox to disable.

public/css/admin.css

@@ -156,14 +156,13 @@ body {
 	z-index: 100;
 	color: #fff;
 }
-#crop_editor input {
+#crop_editor input[type=number] {
 	width: 50px;
 	background: #555;
 	color: #fff;
 }
-.crop_image_container {
-	position: relative;
-	flex-grow: 1;
+#crop_editor input[type=checkbox] {
+	vertical-align: middle;
 }
 .crop_position {
 	background: rgba(0, 0, 0, 1.0);