change "show media previews" wording to "download media previews"

closes #1077

app/src/main/res/values-de/strings.xml

@@ -180,7 +180,7 @@
     <string name="pref_title_show_boosts">Zeige Boosts</string>
     <string name="pref_title_show_replies">Zeige Antworten</string>
     <string name="pref_title_filter_regex">Mit regulärem Ausdruck filtern</string>
-    <string name="pref_title_show_media_preview">Zeige Medienvorschauen</string>
+    <string name="pref_title_show_media_preview">Medienvorschauen herunterladen</string>
     <string name="pref_title_proxy_settings">Proxy</string>
     <string name="pref_title_http_proxy_settings">HTTP-Proxy</string>
     <string name="pref_title_http_proxy_enable">HTTP-Proxy aktivieren</string>

app/src/main/res/values/strings.xml

@@ -202,7 +202,7 @@
     <string name="pref_title_show_boosts">Show boosts</string>
     <string name="pref_title_show_replies">Show replies</string>
     <string name="pref_title_filter_regex">Filter out by regular expressions</string>
-    <string name="pref_title_show_media_preview">Show media previews</string>
+    <string name="pref_title_show_media_preview">Download media previews</string>
     <string name="pref_title_proxy_settings">Proxy</string>
     <string name="pref_title_http_proxy_settings">HTTP proxy</string>
     <string name="pref_title_http_proxy_enable">Enable HTTP proxy</string>