This PR uses the new syntax for commands introduced in Docker 1.13, making it a bit easier to understand just what a particular command is trying to do.
This also pushes the long-form syntax for docker command flags, which are also easier to understand at a glance.
This change allows operators to specify a DOCKER_BIN environment variable. This will specify a binary to run when executing docker, which is useful in cases where the 'docker' command being run must be modified in a way that would otherwise be invasive to Dokku, but minimalistic if done within a wrapper.
While I do not agree with _every_ style change, this will force Dokku to have consistent formatting across all shell scripts, which is arguably a Good Thing™.
The command used to reprocess everything is:
```shell
shfmt -l -bn -ci -i 2 -w .
```
This creates the following commands:
- apps
- apps:create <app>
- apps:destroy <app>
It also:
- makes `delete` an alias for `apps:destroy`
- adds confirmation to `apps:destroy`
- allows a developer to remove apps that have been created via apps:create but have not been deployed
Refs #87
Refs #543
Refs #586Closes#599
Refs #655
Refs #656
Refs #685Closes#757
