Feature to ignore tables that fail to migrate

[drobin04]

I had a use case recently where I had a need to migrate most of the tables from a particular SQL database, where it was acceptable to lose some tables that would fail to convert.

An option to specify that this is fine, and then get a read-out of a list of tables that weren't successful, would be useful.

I was able to work in a checkbox for my own use locally, will try and suggest a clean MR later on when I have something that would be more acceptable for others' use.