S allius/issue387 (#388)

* add optional java script to fetch data regullary

* change file extension to `html.j2` for templates

* fix route for fetch data

- for running in iframes (e.g. HA ingress) we must
  use relative path in the URLs

* increase test coverage

* remove unused statements

ha_addons/Makefile

@@ -88,7 +88,7 @@ SRC_FILES := $(wildcard $(SRC_PROXY)/*.py)\
  $(wildcard $(SRC_PROXY)/gen3/*.py)\
  $(wildcard $(SRC_PROXY)/gen3plus/*.py)\
  $(wildcard $(SRC_PROXY)/web/*.py)\
- $(wildcard $(SRC_PROXY)/web/templates/*.html)\
+ $(wildcard $(SRC_PROXY)/web/templates/*.html.j2)\
  $(wildcard $(SRC_PROXY)/web/static/css/*.css)\
  $(wildcard $(SRC_PROXY)/web/static/font/*)\
  $(wildcard $(SRC_PROXY)/web/static/font-awesome/*/*)\