fix: rename some constraints per wutta model

we will not (yet?) be able to "inherit" from the wutta model Base
which means basically the two are "not related" at this point.

but we do want to *match* whatever wutta has defined so far. the
rattail auth tables may contain more columns but will at least include
those columns present for the wutta model.

part of matching is the constraint names, which have been manually
specified in rattail for a while now. finally wutta has bothered to
define a proper naming convention so we can simply omit the names for
future changes. however it also means we must add an explicit
migration for any models we must match to wutta, to abandon the names
we had previously set which are now "incorrect"

most constraint names can remain as-is i think, since most tables will
never exist in the wutta model. eventually might be good to rename
all at once but that can wait

fix: refactor code so most things work without sqlalchemy

also refactor tests to help ensure that remains true

Move tests out of the installed package set

this seems to be better practice. from what i can tell this is a
clean move with no breakage.. and built package files no longer seem
to include test modules

Make 'tests' a proper subpackage again; add some tests

Trying to make more of an effort here...

General header / Unicode cleanup.

This hopefully updates all module headers such that the file encoding is
utf-8, and uses Unicode literals, etc.