Remove old page templates before updating

Some files may not be removed if renamed during development process. The postinst script will now remove all older templates during the upgrade process.

src/deb/hestia/postinst

@@ -69,6 +69,7 @@ if [ ! -z "$BACKEND_PORT" ]; then
 fi
 
 # Update Web and DNS templates
+rm -rf /usr/local/hestia/data/templates/*
 cp -rf /usr/local/hestia/install/ubuntu/18.04/templates/* /usr/local/hestia/data/templates/
 
 exit 0