Throw exception if package is not found. This makes it more clear when a config error is made.

On a config error (package name not correct) one gets 'package removed' iso 'package not found'

Author: RubenWillems

project/WebDashboard/Plugins/Administration/PackageManager.cs

@@ -101,7 +101,11 @@ public List<PackageImportEventArgs> InstallPackage(string fileName)
                 fileName);
             FileInfo packageDetails = new FileInfo(packagePath);
             List<PackageImportEventArgs> events = null;
-            if (packageDetails.Exists)
+            if (!packageDetails.Exists)
+            {
+                throw new Exception(string.Format("Wanted package {0} not found in : {1}", fileName, ProgramDataFolder.MapPath("Packages")));
+            }
+            else
             {
                 // Load the package and install it
                 events = new List<PackageImportEventArgs>();