Issue/186 WriterSelector to return MimeType of selected Writer

This just PR just undoes commit 9b02511b4df4b39354d23bf027f5289b325b7591 "remove syntax from Readers and Writers.", which lead to issue #186 . This is a pretty sane way of solving this problem, and fits with code already in production for a long time. Please commit this with PR #185 "release/0.7" before making a new release.