Enable expires, headers and cache apache modules

Dockerfile

@@ -39,8 +39,11 @@ RUN a2disconf other-vhosts-access-log
 ADD apache/wordpress.conf /etc/apache2/sites-enabled/wordpress.conf
 RUN echo "Listen 8000" > /etc/apache2/ports.conf
 
-# configure mod_php
-RUN a2enmod rewrite
+# configure mod_php. apache2ctl -M can be used to list enabled modules
+RUN a2enmod rewrite && \
+    a2enmod expires && \
+    a2enmod headers && \
+    a2enmod cache
 RUN crudini --set /etc/php/7.0/apache2/php.ini PHP upload_max_filesize 500M && \
     crudini --set /etc/php/7.0/apache2/php.ini PHP post_max_size 500M && \
     crudini --set /etc/php/7.0/apache2/php.ini PHP max_input_vars 1800 && \