Embedded models in schema

The end of the schema tree is a little messy at the moment with the following options:
 - imported_solids
 - turbine_model
 - traffic_model
 - ocean_biology
 - ocean_forcing
 - reduced_model
 - porous_media
 - implicit_solids
 - embedded_models

A number of these can easily by added to embedded model (ocean_biology, turbine_model, imported_solids, porous_media, implicit_solids), I think.

Ocean_forcing is a bit odd - it's not really an embedded model. Options are to move it to material_phase (separate formula per material phase useful?), leave it where it is, add a new option: ocean_model_options, or just add it to embedded_models

Within ocean_forcing there's a bit of a mish-mash of stuff:
 - iceshelf-meltrate
 - shelf
 - external_boundary_conditions
 - bulk_formulae
 - tidal_forcing

Should the shelf options be moved to embedded models or are these options to do with forcing the ocean surface? I would also like to rename the external_data_conditions as that is very generic, when it is actually NEMO forcing

I think this might need a mini-sprint (on a branch possibly) of all people involved in these projects to make this work as there are a lot of inter-dependencies and flml files to edit.