Support multiple layers of abstract commands

[jamesreprise]

Problem to Solve

Right now, we can't have multiple layers of abstract commands easily, due to our expectation that each class must have a token that cannot contain spaces. For example:

user password set <username>

is difficult to implement.

Proposed Solution

• Allow spaces in tokens.
• Allow multiple levels of abstract classes (this would maintain the same structure in code as in the interface).