Fixed "none" language handling

* There is no `nil` or `" "` magic for labels without language anymore. The new consensus is `"none"`.
Fixed language independent /collection uri
Fixed bugs introduced by "none" language

See @2ed0d043a04e74686cd992f4ea544f5f3163a610
Merge branch 'master' of github.com:innoq/iqvoc into none_language
Fixed some ref uris without language
fixed trailing whitespace

brew uninstall netbeans /cc @tillsc
One more `'none'` => `nil` mapping for language parameters
Merge branch 'none_language' of github.com:innoq/iqvoc into none_language
Added collection pref_label validations

See #168
Needed `rdf_collections` route for ref prefixes
Fixed tests lacking language in URI
Merge pull request #173 from innoq/none_language

Labels without language
Merge pull request #168 from innoq/collection_labels

collections can exist without a primary language
Fixed dashboard rendering of concepts without labelings

See #167
Typecasting symbols as strings in configuration

See #162
Belongs to #128
UI uses square brackets for "translation missing" texts
Merge pull request #162 from innoq/language_configuration_symbols

 instance configuration can't cope with symbol values
Merge pull request #167 from innoq/dashboard_concepts_without_labelings

fallback for label in dashboard
Merge pull request #128 from mrsellars/fix_for_160

missing jQuery UI image assets