Move ApiType to the Danbooru namespace to prevent circular includes

Adjust all signatures to match for this change

src/libdanbooru/danbooru.h

@@ -22,6 +22,8 @@
 
 #include "libdanbooru_version.h"
 
+#include <QObject>
+
 /**
  * @brief The Danbooru namespace.
  * @file danbooru.h
@@ -30,6 +32,15 @@
 namespace Danbooru
 {
 
+enum ApiType {
+    OriginalDanbooru = 16,
+    KonachanDanbooru = 32,
+    Gelbooru = 64,
+    Unknown = 128
+    };
+
 } // namespace Danbooru
+Q_ENUMS(ApiType)
+Q_DECLARE_METATYPE(Danbooru::ApiType)
 
 #endif // DANBOORU_H