KubeMQ chart quality of life improvements

[lhriley]

This PR aims to solve some problems that we were having with deploying KubeMQ via the existing chart. There are numerous improvements that I'll attempt to outline below:

• Add support for nodeSelector, affinity, tolerations: This was required in order for us to place our pods in a deterministic way.
• Move token into a secret, add support for providing license data: This is the prescribed k8s way to manage sensitive data. Also provides a facility for offline license validation which was documented, but difficult to find and not supported by the existing chart.
• Added support for generating a configmap with arbitrary environment variables. This is useful in defining options that are not directly supported by the helm chart.
• Enabled the use of more specific (fullname) resource names. This is pretty common in other charts, and better enables users to define distinct KubeMQ clusters within a common namespace. The default behaviour should be consistent with the existing naming convention by setting both nameOverride and fullnameOverride to kubemq-cluster. Setting these values to "" will use the calculated names.
• Adds annotation support for the statefulset pods.
• Updated the README to reflect these improvements.
• Bumped the chart version to 0.2.0.

[kubemq]

@lhriley , I would like to thank you for this PR,

[lhriley]

@kubemq my pleasure. Thanks for accepting it :rocket: