g3_fit: Always return a parameter table, regardless of model type

[lentinj]

Both gadgetplots & g3_fit_inner() assume the parameters are in table format, not list. But depending which path the model goes through g3_fit(), it may return a list.

Add tests to ensure we always send a data.frame downstream. Note that the R model is fine with a data.frame params now, and once I'm feeling brave enough will switch it's parameter template to be a table, removing the old list template entirely.

report_detail is also a historical artifact that needs tidying up, but one thing at a time. It defaults to 1 anyway, and we automatically turn reporting off when optimising. But it's also being a flag to show that g3a_report_detail() has been added to the model, which isn't easy to check otherwise.

[MikkoVihtakari]

I'll let you merge this...The output of g3_fit() previously also had attributes which are used in the html documents to fetch data on model iteration process: https://github.com/gadget-framework/gadgetplots/blob/18f46a37c2b718228d301b9d8a35d8480d2d074c/inst/nea_ghl.Rmd#L3

These attributes seem to have disappeared in the version I used. Not sure whether they'll reappear after merging this pull request.

[lentinj]

These attributes seem to have disappeared in the version I used

It's a related problem. Looks like summary is added by g3_optim, but g3_fit may rebuild your model / parameter table, in which case they get lost.

They should be fixed by this (admittedly as an unintended side-effect) as the returned parameter table isn't recreated any more. I'll give it a try & see.

[lentinj]

@willbutler42 any objections to this? In retrospect banning g3_fit from accepting list params might be over-eager, but I'm pretty sure it doesn't work anyway.

[willbutler42]

No objections!