Move models into separate repos

[tomdurrant]

At the moment, there is a single install of the rompy model, however a user may only require one model and may not want to install all the additional dependencies associated with different models. This will only become more prevalent as more models are added. It is proposed that that the model config objects and associated templates be moved into stand alone repositories.

[tomdurrant]

As part of this migration, we would want to implement a selective install in the main rompy package to allow multiple models to be installed along with the base package in a single install.

[tomdurrant]

We may also want to investigate a registration process so that valid config options are updated based on installed models

[rafa-guedes]

we would want to implement a selective install in the main rompy package to allow multiple models to be installed

We can set this up in pyproject.toml by defining new [project.optional-dependencies] entries called swan, schism, etc which would install the respective libraries. Then, to install rompy plus all individual models, one could just run

pip install rompy[swan,schism]

[tomdurrant]

This will be closed by #196