Emancipate sites from `builder`
Kwant is moving in a direction where sites and the associated families and symmetries are becoming first-class concepts that are independent of the builder module.
As a first step in this direction, let's move Site
, SiteFamily
and Symmetry
from builder
into system
. (the old names will have to remain usable for backwards compatibility.) SimpleSiteFamily
can be also moved and perhaps renamed.
This will allow to make the lattice
module independent of builder
. This in turn will allow the use of concepts like TranslationalSymmetry
inside the builder module (currently this is impossible due to circular imports.)
With site families independent of builders VerySimpleSymmetry
can be replaced by TranslationalSymmetry
in the builder tests.