Unittest Intensification

[KEggensperger]

We need unittests that test whether a) Intensification really trades off time used for model building and intensification b) a) still works when we use predicted runtimes, i.e. the target run returns a cost value and has not used this amount of time, but we want SMAC to believe the returned cost value

[mfeurer]

@franchuterivera also left a few more suggestions in #663