Removing global state

[marcoeilers]

Removing global state in order to be able to run multiple instances of Silicon in parallel (which several frontends would like to do). Depends on Silver PR viperproject/silver#600

We're making the following changes:

• Adapting to Silver changes, in particular, the fact that FastParser is no longer a global object
• Moving Verifier.program, Verifier.functionData, and Verifier.predicateData to the State class, and passing them from there through the code where needed.
• Verifier.inputFile is removed completely. We're explicitly setting it in the MultiRunRecorder and passing it to the runVerifier method; it's not used anywhere else.

Note that Verifier.config remains global, since I'm assuming that we don't want to run Silicon with different settings at the same time, and it's referenced all over the place

[mschwerhoff]

Thanks for removing the global state! Looks all good to me, modulo the few (and exciting) comments I left.