u/danielw/dm-1395

Creating PR for reviewing DM-1395
Why dos `qserv_css` need such special treatment? Could the same be achieved just by adding a new product, something like:
```python
      "qserv_css": { 'mods': ['css'],  'libs': ...}
```
and then adding `qserv_css` to `libs` in `_czarLib` and `_cssLib` (and removing `'shmods'` and logic below that handles it)?