Custom task fixes

- ChangeSetDelegate.customchange : use change.setClasss instead of direct assignment, the setter instantiate the custom change class.

- CustomProgrammaticChangeWrapper : add annotation which is required by liquibase infra, change ancestor to CustomChangeWrapper to use implementation which is needed for check-sum generation

- Align custom task and custom pre condition to use same parameter className. I found it confusing and even in this repo there was a mistake.

Thx, Avihay