Internationalization for public errors

Currently, we throw many public exceptions without proper i18n.
Wrap natural-language error messages in _() so they can be translated.

In the service plugin, raise NotFound errors using handle_not_found helper
so the error message contains the offending service.

Use ScriptError instead of NotFoundError in bindinstance install.

https://fedorahosted.org/freeipa/ticket/1953

ipalib/plugins/dns.py

@@ -2617,8 +2617,7 @@ class dnsrecord_del(LDAPUpdate):
                         attr_name = unicode(param.label or param.name)
                     except:
                         attr_name = attr
-                    raise errors.AttrValueNotFound(attr=attr_name,
-                                                   value=val)
+                    raise errors.AttrValueNotFound(attr=attr_name, value=val)
             entry_attrs[attr] = list(set(old_entry[attr]))
 
         del_all = False