Loop functionality ideas

When designing the Loop functionality, take the following requirements into account:

1. Iteration index (part of Iterator)
   • Index of int or qint64 value, possibly optional, as it may not be relevant for Foreach with an infinite number of iterations
2. Forever
   • Like while(true)
3. Until (dynamic condition)
   • Like while(condition())
4. Simple repeater with static number of iterations
   • e.g. Repeat(5)
5. The repeater with dynamic number of iterations
   • The exact number must be set in iterator's init handler, i.e. when init is called, the condition handler is returned
6. General Loop element, taking an iterator with init and condition handlers (would increment handler be also needed?)
   • Placed in Group as GroupItem
7. Support iterators with unknown number of iterations, like Utils::FileContainer with Utils::FileContainerIterator