Links in auto-generated docs always point to master branch

[jc-harrison]

We now have versioned docs, so there is a live version of the docs site for each release (as well as for the latest commit on master). However, links to github from the auto-generated API docs for flowclient, flowmachine etc. always point to the master branch. Over time, this will lead to incorrect or broken links as the structure of the repo changes relative to a released version.

It would be preferable for the auto-generated docs for released FlowKit versions to have links pointing to the files in the relevant release on GitHub.