Add support for publishing pacts with branches

[bethesque]

• Add user facing option to pact publishing interfaces to support a "branch" property
• Call the Broker API to set the branch for the version in one of the following ways:
  • Quick and dirty hack - add yet another separate HTTP call to the pact publishing code to create the branch version.
  • The "slightly more work but better in the longer term" solution - use the new "all in one" pact publishing endpoint.

Docs for the quick and dirty solution

• Before creating the tags, send a PUT using the pb:pacticipant-branch-version relation from the index with params pacticipant, branch and version.
• If the branch is set, and the broker does not support branches (ie. the relations are not there), raise an appropriate error (or print warning - which ever works best for JVM) indicating that the broker does not support branches, and they should update to Pact Broker version 2.86.0 or later for branch support.

Docs for the long term solution

See #1452

[johnreilly100]

Just to be clear as it stands is there no way to set the branch though the JVM 4.3.x library? Asked the same question in #1501

[uglyog]

It hasn't been implemented yet

[uglyog]

Released 4.3.4/4.2.19/4.1.33