Handle template scan error for a single folder

If an error occurs due to an invalid template.json file when
scanning a folder this exception is caught and logged and then the
next folder is tried. Previously an exception would stop the
processing of all the  other folders so valid templates would not
be available.

src/MonoDevelop.TemplateCreator/MonoDevelop.Templating/TemplatingEngine.cs

@@ -92,7 +92,12 @@ public void LoadTemplates ()
 
 			foreach (string folder in TemplatingServices.Options.TemplateFolders) {
 				if (Directory.Exists (folder)) {
-					settingsLoader.UserTemplateCache.Scan (folder);
+					try {
+						settingsLoader.UserTemplateCache.Scan (folder);
+					} catch (Exception ex) {
+						string message = string.Format ("Unable to load templates from folder '{0}.", folder);
+						TemplatingServices.LogError (message, ex);
+					}
 				}
 			}