* feat: allow hostname override for email notifier
As it currently stands all notifiers utilise `os.Hostname` to populate their titles/subjects.
When utilising Docker with a bridged network if you set the hostname for a container to an external DNS hostname Docker's internal DNS resolver will override said hostname for all containers within the bridged network.
This change allows a user to specify what hostname should be represented in the email notifications without having to change the `os.Hostname`.
* feat: allow custom hostname for all notifiers
* docs: adjust notification hostname flag
* implement rolling restart functionality
bouncing each image individually can ensure that a group of docker
containers launched with docker-compose can stay 100% up during deploy.
* move rolling restart into a function
* honor params.Cleanup
Co-authored-by: Simon Aronsson <simme@arcticbit.se>
* Adds scopeUID config to enable multiple instances of Watchtower
* Adds tests for multiple instance support with scopeuid
* Adds docs on scope monitoring and multiple instance support
* Adds multiple instances docs to mkdocs config file
* Changes multiple instances check and refactors naming for scope feature
* Applies linter suggestions
* Fixes documentation on Watchtower monitoring scope
