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
> How would wp post term taxonomies work for custom post types or any other object type?

Could be something like `wp post term taxonomies --post_type=page`

> The user will not know the tax name as it is not built in and they may not have registered them.

If the user has no prior knowledge about the taxonomy, then how would the user know to look for terms registered to a post?

> Consistencies is not a good reason to remove functionality, even it is different, it is better user interaction.

Consistency is an important attribute to creating interfaces. In this case, we are creating an interface that has some prior art in WP-CLI.

> Above is just a pain to do and most users will not bother.

Show me the data? Seems like a viable way to go about it if you don't explicitly know the taxonomies registered to a post type