CRTK feature query

[adeguet1]

A CRTK client needs a way to retrieve which CRTK commands are supported for a given device. Using ROS, we could enumerate the topics and services within a namespace but this is not portable for any non-ROS CRTK implementation.

We propose to add two ways to query which commands are available:

• has_feature
  • Query for a single feature (string) and returns a boolean
  • Implemented as a service on ROS
• features
  • Query all features available (list or vector of strings)
  • Could be a service or parameter on ROS