Support external mounted partitions

[framps]

As of now only the boot and root partition are saved in normal mode. Partition oriented mode can be used to backup additional local partitions but they have to reside on the same device as the root partition.

It' quite common to have additional data on other external partitions (not on the root device) which also should be saved.

Right now tar and rsync uses option -X which causes them to stay on the same device. Either -X should be removed and all external mounted partitions excluded if they are not included in an option or the included partition will be saved in a following step.