[Actions] Define applicability

Define applicability of Move/Copy/Link using appliesTo, to avoid
errors being thrown due to lack of context during instantiation.
Addresses immediate cause of nasa/openmctweb#120.

platform/entanglement/src/actions/AbstractComposeAction.js

@@ -122,6 +122,14 @@ define(
             });
         };
 
+        AbstractComposeAction.appliesTo = function (context) {
+            var applicableObject =
+                context.selectedObject || context.domainObject;
+
+            return !!(applicableObject &&
+                applicableObject.hasCapability('context'));
+        };
+
         return AbstractComposeAction;
     }
 );