Allow raw SQL with explicit structure changes

[WebFreak001]

scenario:

• you change a column which rorm-cli can't automatically migrate, e.g. it will create a DeleteField and CreateField entry
• you provide raw SQL statements to do the migration without data-loss, while it isn't otherwise supported by rorm-cli

now I want to be able to continue creating future migrations based on the model like it is described with the DeleteField/CreateField, however I want to be able to keep my data with the SQL statement. For this I would need rorm-cli to not actually execute the DeleteField/CreateField, but rather only my raw SQL statement.

structure_safe already exists on the raw SQL statement step, however AFAICT the other steps such as DeleteField and CreateField would still run, causing data loss on my table or requiring workarounds with an SQL statement before and after, basically copying or renaming the data.