Fixed migrations and seeds to work with UG_Programmes and PG_Programmes

Had to add a bit of a hack by adding in 'Legacy' programme classes which still use the old programmes model at a point in the migrations where that's needed (because the new model hasn't at that point been added).
Merge branch 'feature/data-model-pg' of https://github.com/unikent/programmes-plant into feature/remove-live-flag
fix migrations to use fluent query builder