Unified Backups: Add support for creating simple backups

Proposal

Introduce support for creating simple backups (containing everything).

This should rely on existing rake tasks and some refactor to make it easier to test and/or make it easier to extract functionality in the future.

The intended target for this feature is to cover the use-case of 1k reference architure, file system data only (no object storage support)

The integration of the tool with Omnibus / Docker and Kubernetes installation will be handled in separate issues.

The new command should support the following functionality present in existing one in Omnibus :

• Ability to skip backing up some components
  • Current implementation uses SKIP=first,second
  • New implementation TBD
  • See supported components for a list of supported ones
• Ability to specify a custom name for the backup file (or prefix)
  • Current implementation uses BACKUP=newbasename and appends a timestamp at the end
  • New implementation TBD