Execute Tests inside the VM where possible

[aweingarten]

The recent updates to the dev branch allowing front-end and doctor to run inside the VM are spectacular! Need it for behat too!

[grasmash]

It's kind of already there. At least, if you have DVM and try to execute tests outside of the VM, an informative exception is thrown.

[grasmash]

I'm actually considering reverting the changes to the frontend commands and taking the same approach there. I think I'd like to just emit "Please execute this command inside of Drupal VM" rather than owning the process of SSHing in and executing.

Opinions? @aweingarten @geerlingguy

[aweingarten]

I would keep the front-end approach you introduced. It will significantly simplify training. We can simply tell users go run blt to see all your commands and pick the one you need.