fix encoding problem

UTF-8 is assumed. If a file is displayed, unknown characters are replaced by a UTF-8 question mark
move breadcrumbs partial to files
fix diff view encoding error
refactor files controller
add download action to files controller
fix download link in file view
Merge branch 'correcting_files_view_utf8_error' into correcting412_download_of_ontologies_does_not_work

Conflicts:
	app/helpers/files_helper.rb
	app/views/files/_files_file.html.haml
fix error that was introduced by renaming a helper
fix ontology version download link
Compressed dispensable code.
Merge pull request #426 from ontohub/correcting412_download_of_ontologies_does_not_work

Repair of download of ontologies, fixes #412.