Separate backup

Recommended to review by commit as I try to structure it as refactoring goes. My intention is also to use it as tutoring material for some refactoring presentation.
Yes. The current BackupBR class will probably become a module that will be included into the Bootloader::Device class. And the Bootloader::Device will probably become class with looks almost empty and simply includes a lot of modules. Those are mechanism that are "native" to Ruby and used in a lot of Ruby frameworks and libraries.