Added a CommandWithTerm Class (Version 2)

Added new subcommands wp user term and wp post term. 

Created a new pull request to follow contribution guide lines. 

Related #1474 
> The end point is list, add, set, and remove terms from posts and users, with corresponding test coverage.

You told me that this was the end point. I have used time to get to this point and now you are adding new things. What the hell?