This is a basic cleanup change that improves the readability of several

of the larger query-building functions in our model managers. This

mainly centers around:


Consistent naming (q vs. queryset instead of query being used

   for either or qs sometimes being used).


|= and &= instead of q = q | or q = q &.


Doing as much with Q() objects as possible before calling methods

   like filter(...).


Starting with a Q() object before any conditional logic, instead of

   starting fresh inside of conditionals, to avoid potential issues with

   logic being overridden unintentionally.


General formatting improvements to help readability of some logic

   when combining Q() objects.


Using our modern chaining-like formatting for multi-line queryset

   conditionals (chaining filter() and order_by() across lines, for

   instance).


This helps ensure more consistent code going forward, and lays a

foundation for some query optimization work that is coming.

All unit tests pass.