Aligning barcode config format with barcode generator.

Broke up tests
I would argue that using `AndroidPreferences` is better for tests than using SharedPreferences. Even though `AndroidPreferences` isn't the code under test, using `AndroidPreferences` directly means that the `AndroidBarcode` tests don't have to know how `AndroidPreferences` is implemented (neither does `AndroidBarcode` implementation). And `AndroidPreferences` should have its own set of tests :smile: