M1 test client: Display API endpoint support summary

[rjb1000]

In order to provide debugging information to the user of the M1 test client, it would be useful for it to be able to interrogate the 5GMS AF and print out a summary of the top-level API endpoints that the Application Function implementation supports.

The OPTIONS method specified in #38 is used to achieve this.

Sample output:

Server product: "5GMSdAF-msaf1.mno.net/17.3.0"
Server subproduct(s): "rt-5gms-application-function/1.1.0"

API path                          | API name                | API version | Supported methods
=============================================================================================
/3gpp-m1/v2/provisioning-sessions | M1_ProvisioningSessions | 2.0.0       | POST