[AltKit] Replaces dedicated AltKit module with shared files across targets

Treating AltKit as a full module resulted in more complexity than necessary, when we really just wanted to share some files between different targets. Now we can share individual files across modules as-needed without AltKit overhead.

AltServer/Connections/ALTNotificationConnection.m

@@ -7,7 +7,8 @@
 //
 
 #import "ALTNotificationConnection+Private.h"
-#import "AltKit.h"
+
+#import "NSError+ALTServerError.h"
 
 void ALTDeviceReceivedNotification(const char *notification, void *user_data);