Updated LoadBPARules script

Added message boxes to ask for confirmation to overwrite the existing BPARules.json file (if it exists).

BestPracticeRules/LoadBPARules.cs

@@ -0,0 +1,23 @@
+System.Net.WebClient w = new System.Net.WebClient(); 
+
+string path = System.Environment.GetFolderPath(System.Environment.SpecialFolder.LocalApplicationData);
+string downloadLoc = path+@"\TabularEditor\BPARules.json";
+string url = "https://raw.githubusercontent.com/microsoft/Analysis-Services/master/BestPracticeRules/BPARules.json";
+string dlMessage = "Downloaded BPARules.json. Please restart Tabular Editor.";
+
+if (System.IO.File.Exists(downloadLoc))
+{
+    if (System.Windows.Forms.MessageBox.Show("Would you like to overwrite the existing BPARules.json file?","Overwrite Existing BPA Rules",System.Windows.Forms.MessageBoxButtons.YesNo,System.Windows.Forms.MessageBoxIcon.Warning) == System.Windows.Forms.DialogResult.Yes)
+    {
+        System.Windows.Forms.MessageBox.Show(dlMessage,"Overwrite Existing BPA Rules",System.Windows.Forms.MessageBoxButtons.OK,System.Windows.Forms.MessageBoxIcon.Information);
+    }
+    else
+    {
+        System.Windows.Forms.MessageBox.Show("Did not download BPARules.json.","Overwrite Existing BPA Rules",System.Windows.Forms.MessageBoxButtons.OK,System.Windows.Forms.MessageBoxIcon.Information);
+    }
+}
+else
+{
+    System.Windows.Forms.MessageBox.Show(dlMessage,"Download BPA Rules",System.Windows.Forms.MessageBoxButtons.OK,System.Windows.Forms.MessageBoxIcon.Information);
+    w.DownloadFile(url, downloadLoc);
+}