Using src layout to organize modules (https://packaging.python.org/en/latest/discussions/src-layout-vs-flat-layout/)
This change make it directly detect the package_data import issue of "qeapp.yml" (manifest #255) and css/jinja files in static module.

bumpver

After aiidalab/aiidalab#382, the `setup.py` is not needed anymore.
I remove it.

This PR is separated and prepared for #428 to avoid mixing changes, especially for moving
modules/files without changing any implementations. See #428 (comment)
for the design of restructuring the modules.
It include following changes:

- Move strucute selction to step1 module
- Move modules/folders to configuration folder (step2)
- Move modules/folders to submission (step3)
- Move modules/folders to results (steps)
- move modules/widgets to common folder
- load registred viewer in __init__ to trigger