v3.9.0

! tron.bat:bugfix:  Fix calculation of free space before and after. Was missing code block for post-run space calculation. Thanks to /u/swtester
! tron.bat:bugfix:  Fix a registry modification that mistakenly executed even if the script was in dry run mode (-d)
+ tron.bat:feature: Add -m flag and associated PRESERVE_METRO_APPS variable to preserve default Metro apps (don't remove them). Thanks to /u/swtester
/ tron.bat:misc:    Rename all instances of DO_SHUTDOWN to AUTO_SHUTDOWN