Make check-ui-shell select the first non-current bundle by default

[chrispcampbell]

When running the model-check report in local development mode, we now allow the "baseline" and "current" bundles to be selected in the report header (from whatever bundle files are available in the baselines directory of the project). The first time you open the report, it will show both as "current", which is not very useful. In the case where there are multiple bundles available in the baselines directory, it would be nice if automatically select the first non-current bundle as the baseline, to make it more obvious to the user that they can change it to a different selection.