refactor: key capabilities on href instead of rt

OCF rt is a schema category shared by many unrelated resources.
The stable unique resource address is the href. Update Capability,
discovery, common capabilities, tests, and plan accordingly.

tests/test_common_capabilities.py

@@ -3,9 +3,10 @@ from samsung_appliance.registry.discovery import discover
 
 
 def _reg():
-    return {c.rt: c for c in (
-        common.KIDS_LOCK, common.REMOTE_CONTROL, common.ALARMS,
-        common.ENERGY_METER, common.WATER_METER, common.WATER_FILTER,
+    return {c.href: c for c in (
+        common.KIDS_LOCK, common.REMOTE_CONTROL, common.POWER,
+        common.ALARMS, common.ENERGY_METER, common.WATER_METER,
+        common.WATER_FILTER,
     )}