Improve performance and stability

[bertfrees]

sprint#9 ⏩

Tasks

• Start by profiling the entire application (engine) to see where the biggest problems are (@josteinaj, @bertfrees)
  • We're going to try to work with YourKit. I've done some preparation by writing some "probes": see yourkit-probes daisy/pipeline-build-utils#19.
  • Jostein has already done some profiling before on another script. One conclusion was that Calabash might be a big problem, and that is exactly what I've been suspecting as well.