Remove .get fn names, use third-person in docs

[Frando]

Hi,
while starting to work with willow-rs I noted some things where the codebase differs from the rust naming conventions and documentation conventions:

• In function docs willow-rs uses imperative ("Create a new path") whereas the rust conventions use third person ("Creates a new path")
• A few methods are prefixed with get_, which is discouraged in the conventions. So Path::component_count instead of Path::get_component_count

If there aren't strong reasons for deviating from the convention, I found it to be quite helpful in my coding experience to just stick with it for general consistency and bikeshed avoidance.

[AljoschaMeyer]

Those are on me, I think. I didn't know about those conventions, and these are how I do them usually (exactly for general consistency =D). But I personally am happy to defer to the wider conventions of the rust ecosystem on these points.