add praise to be able to inspect exceptions before unwinding stack

Adding support for [praise](https://github.com/pitr-ch/praise) gem. To be able to investigate hidden exceptions. See [documentation](http://blog.pitr.ch/praise/).
### TL;DR
it creates pry session before stack is unwounded for each `raise` call, stack is inspect-able thanks to `pry-stack_explorer`.

### Quick try
- bundle install
- enable praise in `katello.yml`
- rails s
- drop raise in some before filter
- inspect the error