Task/581 v1 context entities attributes 4ops

### Description
Four new conv ops:
GET/PUT/POST/DELETE /v1/contextEntities/type/TYPE/id/ID/attributes/ATTR_NAME

Why do you have needed to change the SHELL section of this .test? Is related with deprecated "ngsi9/10" URL prefixes... I don't see the relation with the "PUT/POST/GET/DELETE /v1/contextEntities/type/<type>/id/<id>/attributes/ATTRIBUTE_NAME" that are the goal of the present PR.