kqml: Add hot reload support
When working on testing QML snippets, having to save and close and reopen is a drag. This patch adds support to reload any QML when the file on disk changes, making it suitable for rapid prototyping and testing
As it's a relatively new dev tool, this is on by default. We can make it an option if it proves annoying. A behavioural change this introduces is that invalid QML will open a window instead of quitting.
Edited by David Edmundson