[hab] Fix {apply, start, stop} aliases.
[hab] Fix {apply, start, stop} aliases.

This change refactors the CLI alias logic for:

* `hab apply`
* `hab start`
* `hab stop`

The target for all of these aliases were previously satisfied by
external programs (`hab-butterfly` for `hab apply` and `hab-sup` for
both `hab start` and `hab stop`). Now that all of these subcommands are
satisfied by the `hab` CLI itself, these aliases were updated to behave
identically to `hab install`/`hab setup`/etc.

Signed-off-by: Fletcher Nichol <77a0fd9e8048bbacd11af4e957bc6ff03b549f49@nichol.ca>

rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,rsertelon/habitat,rsertelon/habitat,rsertelon/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat,rsertelon/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat