Implements Image Manipulation in Files Page via QueryString

- Extracts the image creation into a service
- Refactors Files Page GET action for better readability and cyclomatic complexity

Oqtane.Shared/Interfaces/IImageService.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Oqtane.Services
+{
+    public interface IImageService
+    {
+        public string CreateImage(string filepath, int width, int height, string mode, string position, string background, string rotate, string imagepath);
+    }
+}