Remove dncommon/ qualifier from dncommon source

Due to a copy/paste error, dncommon/ was referred to in dncommon's
source. This isn't needed since the dncommon.core namespace is already
set.
s/db-spec/db-con/g

Copy/paste typo.
Move create-db-tables to dncommon

The library dncommon is now listed as a dependency for dnserver.
Remove version definitions

The version is already defined in Leiningen's project files, so these
definitions were redundant.