Allow full customisation of probes

[dtomlinson91]

Description
When using the chart the K8s probes should be fully configurable. #29 did some work adding InitialDelaySeconds and periodSeconds, but I can't think of a reason why all probe options should not be configurable by the user.

The chart would be better served by passing any valid probe object instead of a select few options, but at the very least timeoutSeconds, successThreshold and failureThreshold should be configurable for the liveness & readiness probes if passing a probe object goes against the design of the chart.

Basic example
When under heavy load in our environment it can take more than 1s for the health check to complete. I should be able to specify timeoutSeconds for the liveness & readiness probe to something less agressive than 1s.

As it stands I've had to fork the chart and add this in to use the chart in our environment.

Other
This should be fairly straight forward to implement and I'm happy to raise the PR if needed.

[curquiza]

Hello @dtomlinson91

Thanks for the suggestion
Any PR are welcome, thank you very much ❤️