Like the DOS 3.3 sector order issues in #49, this change fixes the
order of the physical sectors on the ProDOS disk when nibblized.
This change also adds tests similar to the DOS 3.3 tests to verify the
sector order.
Because the DOS 3.3 and ProDOS tests are so similar, the utility
methods have been refactored into their own file.
* Adds an initial test for DOS format (.do) files
* Fix physical sector order when nibblizing DOS 3.3 ordered images
Before, when `.dsk` or `.do` images were nibblized, the resulting
track had the sectors in the wrong physical layout.
Now the nibblized track has the correct physical layout (all sectors
in order) which results in the correct DOS 3.3 layout as well.
There is also a test that verifies the order.
* Add another test for a non-zero sector
The new test checks that the values in physical sector 1 are those for
DOS sector 7.
* Add test for all physical sectors on all tracks
This change also removes a few stray console.log calls in the test.
