This makes deploys faster for any that are built from source as the image artifact isn't involved in those cases while also unifying how the file is handled.
Refs #2760
The shorthand is more prevalent in this codebase, and is something that bash supports, so we should just use the same thing everywhere.
Note that we do not use shorthand redirect in Makefile as shell parsing is a bit different in Make and the shorthand redirect doesn't seem to be properly supported, causing CI errors.
This allows folks to later investigate why the rename failed (probably an app bug) and helpfully posts the container logs.
If multiple containers fail, they may have a ton of output, but this is better than not knowing what is going on.
Closes#3900
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 .
```
