Support serving of backend translations (#12453)

* Add view to support backend translation fetching

* Load backend translations from component json

* Translations for season sensor

* Scripts to merge and unpack Lokalise translations

* Fix copy paste error

* Serve post-lokalise translations to frontend

* Linting

* Auto-deploy translations with Travis

* Commit post-lokalise translation files

* Split logic into more helper functions

* Fall back to English for missing keys

* Move local translation copies to `.translations`

* Linting

* Initial tests

* Remove unnecessary file check

* Convert translation helper to async/await

* Convert translation helper tests to async/await

* Use set subtraction to find missing_components

* load_translation_files use component->file mapping

* Remove duplicated resources fetching

Get to take advantage of the slick Python 3.5 dict merging here.

* Switch to live project ID

homeassistant/components/sensor/.translations/season.en.json

@@ -0,0 +1,8 @@
+{
+    "state": {
+        "autumn": "Autumn",
+        "spring": "Spring",
+        "summer": "Summer",
+        "winter": "Winter"
+    }
+}

homeassistant/components/sensor/season.py

@@ -21,10 +21,10 @@ _LOGGER = logging.getLogger(__name__)
 NORTHERN = 'northern'
 SOUTHERN = 'southern'
 EQUATOR = 'equator'
-STATE_SPRING = 'Spring'
-STATE_SUMMER = 'Summer'
-STATE_AUTUMN = 'Autumn'
-STATE_WINTER = 'Winter'
+STATE_SPRING = 'spring'
+STATE_SUMMER = 'summer'
+STATE_AUTUMN = 'autumn'
+STATE_WINTER = 'winter'
 TYPE_ASTRONOMICAL = 'astronomical'
 TYPE_METEOROLOGICAL = 'meteorological'
 VALID_TYPES = [TYPE_ASTRONOMICAL, TYPE_METEOROLOGICAL]

homeassistant/components/sensor/strings.season.json

@@ -0,0 +1,8 @@
+{
+  "state": {
+    "spring": "Spring",
+    "summer": "Summer",
+    "autumn": "Autumn",
+    "winter": "Winter"
+  }
+}