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 .
```
As briefly discussed in #1425, source the `common/functions` file via an
absolute path, rather than determining the relative path by using
`dirname`. 3rd-party plugins should follow suit and use the new
`$PLUGIN_PATH` convention too.
Record events (i.e. pluginhook's calls) as syslog entries and
provide a shortcut command to display the last part of the log
file.
A brief summary of the changes follows:
dokku:
- New DOKKU_EVENTS_LOGFILE envvar to hold logfile location.
plugins/20_events/commands:
- events output log entries, a tail's follow-like mode is
provided too.
- events:[on|off] enables/disables logging.
- events:list lists events that are logged.
plugins/20_events/hook:
- Generic hook that writes log entries. All the events are
registered via symlink to this script.
plugins/common/functions:
- dokku_log_event() writes log entries via logger.
- dokku_log_pluginhook_call() formats log entries and writes
them via dokku_log_event().
