Multiple file input

[MattWindsor91]

Things like regression tests might run faster if Starling can take multiple input files. This would mean we only need to spin up the CLR once, parse the arguments once, and set up the pipeline once.

[MattWindsor91]

So this could either:

1) have the semantics of literally just proving each one after the other, or 2) actually combine the views and methods into one model.

Both modes might be useful. For 2 we would probably need a compositionality result first.