This PR aims to fix some issues regarding scenario onset in Daru. The behaviour of parameter overwrites has been tidied up to ensure
Calibration Y-factors are preserved while scenarios are adjusted so that they are effectively defined with a Y-factor of 1.0, preserving both calibration and scenario values
Parameter overwrites by default have no effect prior to their onset time (previously this was possible due to parameter interpolation)
Parameter overwrites can be defined sparsely within the scenario (i.e. between the first and last times specified in the overwrite, there can be any time points irrespective of what was originally in the parset)
A smooth-onset feature has been added so that scenarios can smoothly begin. Parameter values will be interpolated from the Parset value at start_year-smooth_onset to the Scenario value at start_year. In typical usage, this might mean defining a scenario starting at a time slightly later e.g. a scenario that starts ramping up over 2018 should define its first overwrite year as 2019, with a smooth_onset of 1.0 which will result in the parameter value starting to change at the beginning of 2018
This PR aims to fix some issues regarding scenario onset in Daru. The behaviour of parameter overwrites has been tidied up to ensure
start_year-smooth_onsetto the Scenario value atstart_year. In typical usage, this might mean defining a scenario starting at a time slightly later e.g. a scenario that starts ramping up over 2018 should define its first overwrite year as 2019, with asmooth_onsetof1.0which will result in the parameter value starting to change at the beginning of 2018