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/src/web/wrapper.py

@@ -0,0 +1,26 @@
+from quart import url_for as quart_url_for
+from . import web
+
+
+def url_for(*args, **kwargs):
+    """Return the url for a specific endpoint.
+
+    This wrapper optionally convert into a relative url.
+
+    This is most useful in templates and redirects to create a URL
+    that can be used in the browser.
+
+    Arguments:
+        endpoint: The endpoint to build a url for, if prefixed with
+            ``.`` it targets endpoint's in the current blueprint.
+        _anchor: Additional anchor text to append (i.e. #text).
+        _external: Return an absolute url for external (to app) usage.
+        _method: The method to consider alongside the endpoint.
+        _scheme: A specific scheme to use.
+        values: The values to build into the URL, as specified in
+            the endpoint rule.
+    """
+    url = quart_url_for(*args, **kwargs)
+    if '/' == url[0] and web.build_relative_urls:
+        url = '.' + url
+    return url