Ignore multiple backup directories & logfiles from vsual studio's project conversion.

It is possible to run the project converter multiple times, which would generate new backup-directories (Backup1-Backupn) and logfiles (UpgradeLog2.XML-UpgradeLogn.XML)

Global/VisualStudio.gitignore

@@ -68,5 +68,5 @@ Generated_Code #added for RIA/Silverlight projects
 # Backup & report files from converting an old project file to a newer
 # Visual Studio version. Backup files are not needed, because we have git ;-)
 _UpgradeReport_Files/
-Backup/
-UpgradeLog.XML
+Backup*/
+UpgradeLog*.XML