Refactoring private methods to be protected

[sawtell]

Motivation

Not all imports are simple CSV column to table column mappings. When there are complex relationships as part of the import data the ability to alter the process is required to avoid errors or missing related content.

Changes

Empower users to alter parts of the import process they deem fit by making private methods protected

[tristan-thar]

This is much needed. I tried to run an import of products that have an auto generated UUID. However the package is using the DB facade to insert the rows instead of Eloquent, so no model events are fired, thus the uuid is never generated.
I had to write my own implementation because there was no way to override the private insertRows() function.