Pre and Post script system

[Arminando]

Very often a custom one time adjustment is needed for a rig and instead of creating a rig module for that specific case, it is easier to embed a script that will do the necessary adjustment. These could also be saved into a script library and shared around. The system I would like to make would add a new section into rigify where these scripts can be added and the Pre script would be executed before the rig is built, and the Post one after the rig has been built.

The scripts would need to made with certain requirements in mind. Things like they would need to contain a class with a specific name which would receive the generator object and similar.