Provide the backup routine for final customers

The action points for upcoming release:

• Introduce graceful readonly setting for the cluster (Denis)
• Use this new command within columnstore_backup.sh, rename it to mcs_backup.sh, add the CI test for backup (Allen H)
• Add the script to the engine package, reuse CMAPI bundled dependencies (AWScli, gsutils) instead of forcing user to install it (Allan M, Leonid)

We're still working on the following

• Cmapi Wrapper (Alan) & including the backup script in engine packages (close)
• CI tests ( the current 1 test is inadequate and waiting for the wrapper to be complete to build long term maintainable tests)

Whats done already

• graceful readonly setting for the cluster
• use allens backup script and merging into the columnstore engine repo
• renaming backup script
• wrappers of AWScli, gsutils provided by cmapi
• backup script implementation of new cmapi wrappers of awscli, gsutil

Part of whats extending the timeline is

• Both Allen/Alans Paternity Leave
• Allen keeps adding more functionality to mcs_backup_manager.sh, meaning Alan needs to sync the wrapper