Review load-scripts command line: specify application only

The command line ``load-scripts`` should have an option to load specific module name scripts.

For example:
If we have ``bdc_collectors``, ``myapp`` and ``myotherapp`` registered, and i would like to load only data from ``bdc_collectors``  and ``myapp``:

```py
bdc-db load-scripts --modules bdc_collectors,myapp
```