Add configuration validation and warnings

[lucasmdrs]

As discussed previously here, some sanity checks on the configuration provided should be implemented, to warn the user of unreasonable setup with missing properties and incompatible values (e.g. syncHandlerTimeout being less than kubeClientTimeout)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.