Multi-evaluate

[1313e]

Work on the following:

• Rewrite the Emulator._evaluate()-method and all related methods to take a sample set as the input instead of a parameter set.
  This can potentially significantly improve the evaluation rate of the emulator (especially for large sample set) and make the calculations less susceptible to computational errors;
• Improve the calculations of covariance matrices to use less memory while not reducing its efficiency.
  This is important for both the covariance matrices of the data and a reworked Emulator._evaluate()-method.