- Get just HELM_HOME from .bashrc.

- No more prerun files, remove said code.
- Set PS1 during __prompt (called by BASH_COMMAND everytime the prompt
is going to be shown).
- Consistent calculation of runduration across __prompt and
__command_notifier.
- Open bug: the exit status is shown until a new command is run.

This reverts commit 208c1bcc. Now all
commands are monitored.

- Use notify-send to notify on finished (successfully or not) long
running commands (all commands, not just those with monitor).
- Move all Bash specifics together, under the if shell==bash clause and
to the end.

- Add region alias for configured (profile) region.
- Add metadata-region for outputting the region from the EC2 metadata
service, moved from .bashrc (no longer exported as AWS_DEFAULT_REGION,
not an issue since it could only be used in EC2 instances and not for
local use, it was there mainly as a reminder for me).
- Add ecr-login instead of a shell alias, works the same.

Add the docker remote sub-command (actually the _docker-remote script
but can be invoked as a sub-command with the wrapper script). It creates
a local socket that's forwarded to the dockerd socket on the remote host
via ssh. Requires OpenSSH 6.7 or later (for Unix socket forwarding and
%C token. Typical invocation would be `$(docker remote
host.domain.example)`. A blog post will follow.

Because .bashrc was identified as a plain text file (it's not a shell
script), the shell-lint and shellcheck hooks weren't checking it. Add an
explicit hook just for it. Also, fix or silence whatever shellcheck
found.

So `_docker-dev` could be invoked as `docker dev` without `docker-dev`
getting in the way of tab completion. Renamed the current subcommands
accordingly.