Show vocab tags as normal tags by default

Commit 7766386 changed the default behaviour of vocab tags so that
they are _not_ shown as normal tags (e.g. on the dataset read and search
pages). I thought this was a good idea because it's weird when you use
tag vocabulary to add a custom field, to see that tag also appear in the
normal tags. However, changing this behaviour breaks some tests, so I'm
changing it back!

If an extension is using a tag vocabulary to add a custom field, and it
doesn't want tags from that vocabulary to appear alongside normal tags,
then the extension can add the freet_tags_only converter to the schema
itself.

ckan/logic/schema.py

@@ -196,11 +196,7 @@ def db_to_form_package_schema():
     schema = default_package_schema()
 
     schema.update({
-        'tags': {
-            '__extras': [ckan.lib.navl.validators.keep_extras,
-                ckan.logic.converters.free_tags_only]
-            },
-        })
+        'tags': {'__extras': [ckan.lib.navl.validators.keep_extras]}})
 
     # Add several keys to the 'resources' subschema so they don't get stripped
     # from the resource dicts by validation.