For process parameters, allow any start_year and any end_year (even outside of the milestone years)

[ahawkes]

Describe the bug

At the moment process.rs throws an error if a process start_year is outside the year_range (which I guess is bounded by the first and last milestone year in the input data). This is in the into_parameter function in impl ProcessParameterRaw in process.rs.

To Reproduce

I just read this in the code. But if you have a start_year or end_year for a process that is before the first milestone year or after the last milestone year this will throw an error.

Expected behavior

What we want is for modeller to be able to specify a start_year or end_year that is outside the milestone years range. This just means that a process of that type is available (or not) from the first year onwards, or until the last year. May seem like a possible modeller error, but there is no harm, and indeed existing processes (i.e. assets in input data) may well have been commissioned before the first milestone year.

[alexdewar]

Oops! Thanks for the report. I'll fix this up.