feature #178 German translations for flash messages (xabbuh)

This PR was squashed before being merged into the master branch (closes #178).

Discussion
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German translations for flash messages

This adds German translations for the flash messages added in #163.

Commits
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af2192d German translations for flash messages

Author: javiereguiluz

app/Resources/translations/messages.de.xliff

@@ -199,6 +199,18 @@
                 <source>post.no_posts_found</source>
                 <target>Keine Beiträge gefunden.</target>
             </trans-unit>
+            <trans-unit id="post.created_successfully">
+                <source>post.created_successfully</source>
+                <target>Der Beitrag wurde erfolgreich erstellt!</target>
+            </trans-unit>
+            <trans-unit id="post.updated_successfully">
+                <source>post.updated_successfully</source>
+                <target>Der Beitrag wurde erfolgreich bearbeitet!</target>
+            </trans-unit>
+            <trans-unit id="post.deleted_successfully">
+                <source>post.deleted_successfully</source>
+                <target>Der Beitrag wurde erfolgreich gelöscht!</target>
+            </trans-unit>
 
             <trans-unit id="help.app_description">
                 <source>help.app_description</source>