This change converts existing CHECKS files into a healthchecks key that is understood by 'docker-container-healthchecker'. This tool supports a number of different types of container healthchecks - command, http, uptime - and can perform healthchecks against non-web processes.
The use of the old CHECKS file is now deprecated, and will be removed in the next minor version. Users can use the 'docker-container-healthchecker' to convert existing CHECKS files to the new format automatically.
Closes#2760
Because the app-json extraction happens before the build-dir is set, it doesn't end up respecting the value, and thus the user might get the wrong app.json file.
This takes advantage of path.Join()'s default of ignoring empty paths.
This occurs during the postdeploy on the first deploy of an app, mimicking heroku. It currently happens _after_ the `postdeploy` and `release` deploy tasks.
This functionality enables users to manage a global crontab for the Dokku user that contains all scheduled tasks across all apps. Alternative schedulers can implement cron tasks as desired.
