Provide client access to other microservices

# 🚀 Feature Request

### Relevant Package [**REQUIRED**]

This feature request is for... C Device SDK

### Description [**REQUIRED**]

Provide a facility for device services to easily access other edgex services. Initially this will be REST based

### Describe the solution you'd like
If you have a solution in mind, please describe it.
* expose the existing `endpoint` structure
* provide a function to resolve an endpoint. This will work from cached configuration or the registry, as appropriate
* expose some form of the existing `ping_client` function for checking that a service is running
* provide a function which accepts an endpoint, an api path, a payload and a method; which performs marshalling/de-marshalling and returns the response.
* rework the existing internal clients to use the above
### Describe alternatives you've considered
Have you considered any alternative solutions or workarounds?