Add configuration to remove checking for reversal migrations for each migration file

[SharkFourSix]

Is your feature request related to a problem? Please describe. The way of constructing migration units it kind of problematic because it forces the users of the library to use a certain style (your styles) of doing migrations. I do not want to create a reversal migration unit for each migration file that I create. I can always create another migration file to fix or undo previous migrations at any point in time.

Describe the solution you'd like Add configuration to turn off this behavior