Added support for Mustang (I,II,III-V) V.2 Series

Mustang V.2 series stores backup comments in a file named
"M2_BackupName.fuse" (instead if MU_BackupName.fuse of the V.1 series).
So the previous version of Speed Shop refused loading such backups.
Merge pull request #22 from derwok/develop

Added support for Mustang (I,II,III-V) V.2 Series