improve decision for html or plain text sending of file
use proper http accept record
Improve OWL API request header check

Now, we use accept header ordering computed by
rails. As long as the q-values don't change, in
their ordering, we have more robust code now.

This code is about to be deleted/reverted together with
0a4106958a2950ecde156cacae0e9702dc819867.
Merge pull request #841 from ontohub/hotfix-check_proper_request

improve decision for html or plain text sending of file