WIP: extract loading logic from model

Loading logic should be extracted from the model, to make
loading the data from other sources, such as a local database for
synchronised items, possible.

core/src/support/loader.cpp

@@ -0,0 +1,6 @@
+#include <JellyfinQt/support/loader.h>
+
+Loader::Loader()
+{
+
+}