large commit

change:
* add filter concept
* one can remove / export un-selected compounds
* improved 2d icon renderering

small change:
* openbabel 3d for csvs is computed form smiles/inchi instead from cdk-2d-sdf
* more messages
* rendering of sets: null is ignored for coloring
* mixture handling can be switched on via command line, results are cache in own file

fix:
* domain is stored per dataset (this may cause errors when multiple datasets share common nominal features)
* features computation is repeated if 3d structure is computed by now

rewrite:
* do not store clusters in seperate files
* cache is now independent from relative class path
* cached files are stored in .ches-mapper/cache
* make caching faster