Refactor onRequestNavigation() out of HFrame and HFrameset into framer.onClick.
1. Refactor HFrame#renderFrames (inherited by HFrameset#renderFrames)
    as HFrame#handleChildFrames which passes control to framer.handleFrame()
    to schedule the work.

2. `scope:` rebasing wasn't working (except for <hf:frame src="scope:...">)