Remove unused i18n messages and update description and authors

"propertysuggester" and "propertysuggester-intro" appear to be unused.

I think there was a special page at one point for the suggester and
maybe the messages were used there. We don't need these messages now.

Also added authors and improved the extension description message.

i18n/en.json

@@ -1,8 +1,9 @@
 {
     "@metadata": {
-        "authors": []
+        "authors": [
+            "Christian Dullweber",
+            "Katie Filbert"
+        ]
     },
-    "propertysuggester-desc": "Shows suggested properties for wikibase items.",
-    "propertysuggester": "Property Suggester",
-    "propertysuggester-intro": "This is the PropertySuggester."
+    "propertysuggester-desc": "Suggests properties when adding Wikibase statements."
 }

i18n/qqq.json

@@ -1,8 +1,8 @@
 {
     "@metadata": {
-        "authors": []
+        "authors": [
+            "Christian Dullweber"
+        ]
     },
-    "propertysuggester-desc": "{{desc|name=PropertySuggester|url=http://www.mediawiki.org/wiki/Extension:PropertySuggester}}",
-    "propertysuggester": "Property Suggester",
-    "propertysuggester-intro": "introduces suggester"
+    "propertysuggester-desc": "{{desc|name=PropertySuggester|url=http://www.mediawiki.org/wiki/Extension:PropertySuggester}}"
 }