add Redis cache and some clean up

- update and cleanup in README.md
- update getIdentity to throw response exception with 401 in JwtService
- update http files to use identity from env
- add cacheable to getIdentityFromDevice in DeviceRegistryService
- add RedisCacheConfiguration
- add CacheProperty
- set up cache property
- set up data redis cache

src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -39,6 +39,11 @@
       "name": "device-configuration.url",
       "type": "java.lang.String",
       "description": "Url for device configuration service."
+    },
+    {
+      "name": "cache.time-to-live",
+      "type": "java.lang.Long",
+      "description": "Cache expiration in minutes."
     }
   ]
 }