Rename Jenkins master pipelines

[ghost]

The master/nightly pipelines on Jenkins have names such as Windows-10-2018b, they should be updated to have a more descriptive prefix e.g. Master-Windows-10-2018b or Nightly-Windows-10-2018b.

Having the prefix allows us to identify what the pipeline's purpose is from the name and also allows us to reference all the pipelines using a glob. For example, the Nightly-Trigger pipeline currently triggers all the nightly builds, but these need to be listed manually, and any new pipelines need to be added to the list. If all the nightly pipelines had the same prefix, all the existing, and future pipelines, could be triggered with the glob Master-*.

This should be done in Herbert and Horace and will require an update to the get_build_type function in each of the Jenkinsfiles.