try and improve setup of the templates_c directory for debian

debian/postfixadmin.postinst

@@ -19,16 +19,25 @@ if [ "$(readlink /etc/lighttpd/conf-available/postfixadmin)" = "../../postfixadm
     rm -f /etc/lighttpd/conf-available/postfixadmin
 fi
 
+# Try and avoid templates_c being in /usr/share/postfixadmin and ensure it's writeable by the webserver
+if [ ! -d /var/cache/postfixadmin ]; then
+    mkdir -p /var/cache/postfixadmin
+    chown www-data:root /var/cache/postfixadmin
+    chmod 700 /var/cache/postfixadmin
+    ln -s /var/cache/postfixadmin /usr/share/postfixadmin/templates_c
+fi
+
 # See : https://sourceforge.net/p/postfixadmin/bugs/376/ - remove any existing templates_c files on upgrade.
 if [ -d /usr/share/postfixadmin/templates_c ]; then
-    find /usr/share/postfixadmin/templates_c -type f -exec rm -r {} \;
+    find /usr/share/postfixadmin/templates_c -type f -delete
 fi
+
 if [ -d /usr/share/postfixadmin/templates_c ]; then
     chown www-data /usr/share/postfixadmin/templates_c
 fi
 
 if [ -d /var/cache/postfixadmin ]; then
-    find /var/cache/postfixadmin -type f -exec rm -r {} \;
+    find /var/cache/postfixadmin -type f -delete
     chown www-data /var/cache/postfixadmin
 fi