Support of static attributes in devices app #114
Description
The static_attributes can be specified during provisioning service groups or devices. The static_attributes can be used to represent extra information of the devices, e.g. measuring range, relationship, location, etc. The use static_attributes also has good synergy with the data model. For examples, a service group can be created from a data model and contains several static attributes. Auto provisioned devices under this service group will automatically inherent the static_attributes and will have the same extra information in their entities.