Added a CommandWithTerm Class

Added new CommandWithTerm Class similar to the CommandWithMeta Class.
Designed to reusable for different object types. Currently this is draft and I am still testing it. Just wonder if I was on the right track with this solution. Feedback is requested. I will write tests when I know that I am on the right track. 

Related #1379
> When using plugins, we don't always know the key name (taxonomy name) that you want to modify. Without looking through all the plugin code in the codebase, there is no way to find that find that taxonomy name.

This sounds like a problem we can solve with something like `wp post term taxonomies` (information about taxonomies registered to a post) and `wp term taxonomies` (information about all registered taxonomies.

> This would be different, as I could daisy chain commands.

Can you explain how you'd like to daisy chain commands in greater detail?