itn_irs changing overtime no bump :)

[OJWatson]

1. num_int change
2. num_intworks with base model for pop_split reasons
3. itn_vector and irs_vector changes

[jhellewell14]

Is this fixed?

[OJWatson]

This relates to code that has now been removed. This needed to use the create_r_model code approach because it required altering the equilbirium initial state before being passed to run model. The itn_irs_model that used to be included had this in. I think just close and if/when anyone needs to revisit this then can find the itn_irs model from the commit history etc.