Update geb-saucelabs plugin to use Sauce Connect 4

This pull request includes changes to update the geb-saucelabs plugin to use Sauce Connect 4.

Sauce Connect 4 is a C-based binary distribution (the previous version was Java based), and the zip files relevant to each supported operating system are currently included within the [Sauce CI helper library](https://github.com/saucelabs/ci-sauce).

This change uses the SauceConnectFourManager class to extract the Sauce Connect zip file which is applicable to the current operating system from the ci-sauce.jar file to the current working directory, and return the command line arguments required to launch Sauce Connect.

The change also allows users to supply extra options to the Sauce Connect process, as well as changing the port that Sauce Connect is launched on.

The previous requirement for users to specify the Sauce Connect jar file location is not needed as part of these changes.

Please let me know if there are any problems with the change - I had to include the ci-sauce dependency in several of the build.gradle file in order to get everything compiling.