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
It is associated data with an object, where the key (taxonomy) is not defined by the user but the data is. One of the use cases of meta list function is to find the meta key name. Once that key is found you can then modify the data. 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. 

If there there were a command like this. 
```wp taxonomy <object_type>```
This would be different, as I could daisy chain commands.