gp_emulator: Release of Remote Sensing paper code

This code has been used in the Remote Sensing paper that cites this release (a recursive software release we're dealing with here... No less and no more...). The paper reference is

Gomez-Dans, J L, Lewis, P E, Disney M, "Efficient Emulation of Radiative Transfer Codes Using Gaussian Processes and Application to Land Surface Parameter Inferences", Remote Sensing, 2016