highly contaminated bins should get a warning not to use filtered data even after cleaning

[jvollme]

mdmcleaner is NOT designed to rescue terrible bins. It is only meant to validate good quality and to make good bins better!
This needs to be reflected in the results, so people are not encouraged to publish terrible bins (e.g. >20% contamination) after filtering

[jvollme]

also check the pairwise identities of multi copy rRNA genes. Raise a warning if rRNA gene copies are less than 99% identical, regardless of final classification.