VQkit v1.1

This version promotes the current development build to VQkit 1.1.

Included changes:
- Simplified Mechanical / Structural Materials submenu.
- Quantum ESPRESSO mechanical option [2] now reads variable-whitespace stress headers such as `total   stress`.
- MIT License retained.
- Current VASP and Quantum ESPRESSO workflows preserved.

Installable wheel:
  vqkit-1.1-py3-none-any.whl
