New Feed Wizard: Simplified page flow

- Automatically distinguish between <archive> and <single-file>
- Merged Local and Online pages into Download page
New Feed Wizard: Show Icon page for non-EXE files as well
New Feed Wizard: Support multiple entry points
New Feed Wizard: Fixed ITaskHandler reuse

If a ITaskHandler is reused after the user has pressed a Cancel button all following operations will be canceled right after being started