Integer value sanity

[cjcodeproj]

The Track class code should be updated to ensure that the attributes track_no, track_total, disc_no, and disc_total are properly set as integers values, even if the values are not present in the id3 tags.

A default disc_no or disc_total value should be 1 if not specified, assuming that the CD came on a single physical disc.

A default track_no and track_total value should be 0; which is technically an invalid value, but it satisfies our need to have a value for sorting. An editing flag should be added to the XML to signify that there are invalid track numbers.

[cjcodeproj]

Commit:

https://github.com/cjcodeproj/musicscan/commit/de2ee1a4ed3330e6f7af9469edfb2199f0b8ad43

Closing notes:

• Integer value check was put in a separate class method to keep the code distinct, and easier to modify. The Track class code is likely to change in the future.
• We're casting the values passed from TinyTag into integers, but there is a chance they could already be integers, depending on the version of TinyTag.