Some tech files should live in the "Stackup" object

[jwright6323]

For example, QRC techfiles and technology LEFs are stackup-specific, so these should live in the "stackup" data structure. Right now, if you have multiple stackups, you'd need separate technology JSONs to support that. This is low priority since right now we don't support any technologies with multiple stackups, but we should fix it before we build too much infrastructure with the current APIs.

[jwright6323]

Also, obligatory comment that this relies on #308

[jwright6323]

Bumping the priority here, as it's an annoyance for building new plugins. The QRC techfile should definitely not be a library-specific thing.

[jwright6323]

Also, funnily enough, the tech LEF is an independent library and one could argue it belongs with the std cells, although I think it's also reasonable to keep it separate.