add an "afterImport" hook to the importer process

[notscottsmith]

The aim is to display a table of "to be imported" results prior to importing to be able to, if the user wants, manually change and/or affect the data prior to it being inserted into the database.

Alternatively, adding the ability to add the importer() function or a variant of to the wizard action so that the same can be achieved with a multi-step import process.