S allius/issue395 (#399)

* add button for languages setting

* build a web module for the dashboard

- load all python module from local dir
- initialize Blueprint and Babel

* set a default key for secure cookies

* add translations to docker container

* improve translation build  

- clean target erases the *.pot
- don't modify the resurt of url_for() calls
- don't translate the language description

* translate connection table, fix icon

* build relative urls for HA ingress

* fix unit test, increase coverage

app/entrypoint.sh

@@ -23,7 +23,7 @@ if [ "$user" = '0' ]; then
     echo "######################################################"
     echo "#"
 
-    exec su-exec $SERVICE_NAME "$@"
+    exec su-exec $SERVICE_NAME "$@" -tr './translations/'
 else
     exec "$@"
 fi