we need a better way to do progress notification for various actions.
A simple usecase is a user action or filter that can be split into multiple
subactions which each have their independent progress indication.
We want to show the total progress in a progressBar.

This new class does that and all of the following features:
* threadsafe
* be able to handle more than one concurrent action
* be safe
* be cancelable
* non-modal
* be fast
* be really easy to use

svn path=/trunk/koffice/; revision=599863