Fix version number for tarballs

re-tagged v2.18.0

set correct 2.16.0 release version strings

Updates for NEST 2.14.0 release

Merge pull request nest#666 from heplesser/fix-665-topoconnect

Connecting to layers of recording devices now works properly

Release of v2.10.0

Release of v2.8.0

Dry-run mode freshly arrived in git repo structure

version 2.6.1