Allow only creating work items for the tested repository, not any of its dependencies

I'd like to be able to create a nightly CI run that configures and builds just qt5.git top-level build, without having to configure / build / wait for any submodule dependencies.

Waiting for the dependent work items in this case doesn't make sense, because the qt5.git top-level build won't use them.

I'm thinking it should be possible to permanently configure this behavior in the platform configuration file, as well as per-run in the scheduler as a new Coin Feature.

So if a coin/platform_configs/nightly_top_level.yaml file contains a "NoSubmoduleDependencies" Feature, and i schedule a build of qtsvg.git against the platform, it would create work items just for qtsvg, not qtbase.

If i schedule it against qt5.git, it would create work items for just qt5.git (both build and test).

I think logic for this behavior should already exist in Coin, because I think that's partially how the LicenseTest work items are created.