Change add/update functions to have a consistent naming scheme and behaviour

[stevencarlislewalker]

Proposal:

• use create_* when adding a component to a model that doesn't yet have that component
• use replace_* when overwriting an existing component
• use append_* for 'list components' (e.g. add_rate should be append_rate, vec_rate should be append_vec_rate)
• use remove_* for removing items from 'list components'
• use edit_* for modifying values of existing list/vector components (e.g. edit_params(beta = 0.2) instead of update_params(beta = 0.2)) -- not sure if there should be an edit_rate for modifying the formula for a particular rate
• use reset_* for returning a model component to the default (typically this is a NULLish object like a zero-row data frame or a zero-length list)

Perhaps append_* should just be kept as add_* to minimize changes?

Perhaps there is no difference between create_* and replace_* and the latter is better?

Every model component should have all applicable verbs defined.

[stevencarlislewalker]

FYI @papsti , @wzmli , @Flynn-Primrose , @evanjmitchell. Comments would be welcomed.

[evanjmitchell]

I think that all sounds good. For me personally the only point of confusion was add vs. update, but changing update to edit fixes that I think. I agree that you could just keep add to minimize changes (instead of changing it to append).