reuse callbacks, default table/column names, & unique combinations

The library is great but to integrate it into a project I am working on I needed to add unique combinations and that I could restart the loaders to working with callbacks more than once.

While adding that I made it so that I could use the variable names and class names as the column names and table names respectively by default if no argument is given to @column or @table

I hope that you and the rest of your library's users find these modifications useful