Improve diode LEF files.

 * Add `USE` and `SHAPE` properties.
 * Remove `CORE` class.
 * Fix layer for power pins.

Fixes https://github.com/google/skywater-pdk/issues/141.

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>
tree: 73cfc10dc1c1130222857c351f7f7428ea97dc30
  1. .gitignore
  2. LICENSE
  3. README.rst
  4. cells/
  5. models/
  6. tech/
  7. timing/