Mdshare

- updated file catalogue

upcoming
- removed obsolete/unsused imports/variables/...
- replaced assert statements

- added progressbars
- major refactoring to have an offline catalogue available
- allow to download/extract .tar.gz containers

- replaces FTP usage

- updates to documention and package

- provides `mdshare.catalogue()` and `mdshare.search()`
- deprecates `mdshare.load()`
- provides `mdshare.fetch()` as successor to `mdshare.load()`

- removing numpy dependency
- code cleanup