Topology Validation in Knox CLI

Topology configuration or misconfiguration are common support cases and pain points for users of Knox.

Create a new command in the Knox CLI utility to check the validity of a topology file.

Not specifying /path/to/file could default to /etc/knox/conf/topologies/default.xml.
This feature should allow a user to test the syntax of a topology file, a "shallow" validation. It does not have to check the validity of the contents.

This feature would also become part of the Knox support checklist in support and would speed up time to resolution when.