Ready for MERGE:  Add command to import preprocessed data

Tests will not pass until @josenavas issues a new pull request. 

Also, add ```required=True``` for required options.  So, this, instead:
```python
from qiita_db.util import get_filepath_types
# snip ...
@click.option('--filepath_type', help="Describes the contents of the input files", 
             required=True, type=click.Choice(get_filepath_types().keys())
```