create_ensemble: Internal function to create the ensemble
In spartan: Simulation Parameter Analysis R Toolkit ApplicatioN: 'spartan'

Internal function to create the ensemble

create_ensemble(ensemble_emulations, all_emulator_predictions,
  emulator_test_data, measures, emulator_types, pre_normed_mins,
  pre_normed_maxes, algorithm_settings = NULL, normalise = FALSE,
  timepoint = NULL, output_formats = c("pdf"))

`ensemble_emulations`	All emulations to build into the ensemble
`all_emulator_predictions`	Test set predictions from all emulators, on which the ensemble will be trained / emulators weighted
`emulator_test_data`	Data on which the ensemble performance will be assessed
`measures`	Simulation responses the model should predict
`emulator_types`	Machine learning techniques being employed
`pre_normed_mins`	The minimum values of each parameter prior to data normalisation. Used to rescale the results
`pre_normed_maxes`	The maximum values of each parameter prior to data normalisation. Used to rescale the results
`algorithm_settings`	Object output from the function emulation_algorithm_settings, containing the settings of the machine learning algorithms to use in emulation creation. Used here to obtain settings relevant to ensemble creation - namely number of generations and whether the ensemble should be saved to file, as well as whether plots should be produced showing ensemble performance.
`normalise`	Whether the predictions generated when testing the ensemble should be normalised for presenting test results
`timepoint`	Simulation timepoint for which an ensemble is being created
`output_formats`	File formats in which result graphs should be produced