Include option for stemcell patch version

[ddieruf]

Currently a stembuild only uses the major and minor parts of semantic versioning when building a stemcell. This pipeline uses that as a name for the corresponding VM. As a result, it overwrites any existing VM with the same name as it runs.

An example would be when the pipeline has successfully processed stembuild version 2019.14 there is a VM named "2019.14". When windows update is run but the stembuild version is the same, that "2019.14" VM is overwritten.

A new option with the stembuild package command is to include a -patch-version. This will result in using the patch number of semantic versioning. So the VM name would be "2019.14.1" and then when the pipeline is run again it could iterate to "2019.14.2" then "2019.14.3" and so on.

This patch version number is not read by Cloud Foundry (OpsMan) when uploading the stemcell. All it cares about is the major and minor version number. But it does help an operator to track which stemcell has been deployed on which foundation.

[ddieruf]

During the clone step, the pipeline will look for existing VMs (name) using the intended major and minor version. If none then the cloned VM name will have a .0 patch version added on to its name. If >0 then the collection of VMs found to be sorted based on the patch version number and the new cloned VM name will have an (n+1) patch version based on the highest number in the collection.

If the operator chooses to not manipulate this numbering then each time update is run on the current stembuild version, the patch version should be 0, 1, 2, ... . The operator can change the VM name to something like "2019.4.10". The pipeline will honor that and the next VM created with the same stembuild version will be "2019.4.11".