Allow destructive schema changes

[jeromegn]

If a user knows what they're doing, they should be able to make destructive changes to the schema.

This is the UX I am imagining:

corrosion reload --allow-destructive table_name.column -d table_name2.column

... and this would add the appropriate fields on the API request to create a schema update that allows destruction of these specific table + column combos.