Add support for batching

[sol]

This is useful when you want to distribute a test run over multiple nodes.

• --number-of-jobs=n will define the number of nodes.
• --job=n will select a specific batch to run (n should be the node number)

We wand to deterministically shuffle the tests before dividing them into batches so that it's more likely that each batch will require a similar amount of time to complete (I'm assuming here that it's likely that slow tests are close to each other, e.g. a specific part of an app may be slow to test).

If anybody has suggestions / feedback / thoughts, please comment here!