minor #270 Added Polish translations (jzawadzki)

This PR was merged into the master branch.

Discussion
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Added Polish translations

Polish translations for `previous`, `next`, and `save and create new`.

Commits
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43e384a Added polish translations

Author: javiereguiluz

app/Resources/translations/messages.pl.xliff

@@ -18,6 +18,14 @@
                 <source>mit_license</source>
                 <target>Licencja MIT</target>
             </trans-unit>
+            <trans-unit id="previous">
+                <source>Previous</source>
+                <target>Poprzednia</target>
+            </trans-unit>
+            <trans-unit id="next">
+                <source>Next</source>
+                <target>Następna</target>
+            </trans-unit>
 
             <trans-unit id="title.homepage">
                 <source>title.homepage</source>
@@ -104,6 +112,10 @@
                 <source>label.create_post</source>
                 <target>Dodaj artykuł</target>
             </trans-unit>
+            <trans-unit id="label.save_and_create_new">
+                <source>label.save_and_create_new</source>
+                <target>Zapisz i dodaj kolejny</target>
+            </trans-unit>
             <trans-unit id="action.back_to_list">
                 <source>action.back_to_list</source>
                 <target>Powrót do listy artykułów</target>