Slighly modify Sort parsing: avoid building MultiplSort() instances
comptised of a single sort, but return that sort instead, since it wraps
things with any gain.
Include import of __future__ features division, absolute_imports and
print_function everywhere. Don't add unicode_literals yet for it is
harder to convert.
Goal is smoothing the transition to python 3.
Some weird behavior was possible when having two iterators on the same Results
object. May seem far-fetched, but it is possible. As an added bonus, this
saves a little memory by disposing of rows when they have been materialized
into model objects.
Remove all formatting related code from models. It now lives in the
`FormattedMapping` class. Only API change is from `model.formatted` to
`model.formatted()`.
* sort can be sepcified using the 'field_name'(+|-) syntax
* supports fixed fields and flexible attributes
* includes plugins fix for API changes (might have missed some)
In preparation for #660, where we will allow MediaFile to expose None values
when tags are missing (and consume None to remove tags). This makes it
possible to hide nullness in the rest of beets by translating None to a
suitable zero-ish value on field assignment.
Types can of course opt out of this to preserve a distinct null value. We do
this now for the album_id field, which needs to be null to indicate
singletons.
Type.normalize() also enables more sophisticated translations (e.g., an
integer field could round off float values assigned into it) in the future.
