Import validation allows loose taxonomy

[dleehr]

Within a project, datasets must have the same root taxon level (IcznGroup). Otherwise, the search does not display the taxonomy correctly and data is not found.

So the first issue is that the application will import data that cannot be searched. This is easy to reproduce by uploading two datasets into a project with different taxonomy levels (e.g. one starts at kingdom and the other starts at htg)

[dleehr]

This is related to #116 and should be improved by #119.