Mdmcleaner

- adjusted download and construction of reference database to current gtdb update
- changed setup.py to exclude duplicate mdmcleaner.py script
- temporary fix for problems with "silva_conflict"
- other minor changes

- fixed bug that prevented rerunning "clean" workflow on finished (or partial) previous runs
- some minor changes

first release that is also present in bioconda.

some changes:
- better error messages e.g. if reference databse is not set or can't be found
- fixed bug that prevented manual naming of output folders
- fixed paths under which the global 'mdmcleaner.config' and 'blacklist.list' files are expected
- only requirements for the actually used workflow are now checked

v.0.8.0
the first release that is available on pip!