Custom task fixes

[AvihayTsayeg]

• 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.

[tzachz]

did you intentionally fork this to your own account and not Kenshoo's?

[AvihayTsayeg]

No, we already have a repo with that name it did not allow me to do it.