named args: Warn when user references a formula with the same name as a cask

[whoiswillma]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

Print a warning/suggestion when a formula is referenced with the same name as a cask.

In brew home, when a user opens the homepage of a formula that has the same name as a cask, homebrew prints a helpful message telling the user to load the homepage of the cask using brew home homebrew/cask/<cask>. This PR generalizes that to all formula/keg/cask loading.

e.g. brew home crunch prints

Treating crunch as a formula. For the cask, use homebrew/cask/crunch
Opening homepage for Formula crunch

e.g. brew upgrade crunch prints

Treating crunch as a formula. For the cask, use homebrew/cask/crunch
Warning: crunch 3.6 already installed

Next Step

After this PR, I plan to submit a PR that adds commented-out deprecations for cask commands that have already been integrated with brew

[MikeMcQuaid]

Great work as usual @whoiswillma!