Merge prev-page/next-page into a navigate command.
Update docs
Adjust comment
browser.commands: Refactor :navigate.
Add :navigate up
Add increment/decrement to :navigate
commands: Move tab opening to _open functions.
Split :navigate into several functions
Fix commands with ignore_args=True (e.g. :restart)
Split docutils from utils
Update BUGS
Add qute:settings handler

Add a helper page to help users change settings without having to edit a config
file or remember a bunch of :set commands. This is a rough draft for
discussion. It still needs some improvements to how it handles some
non-standard types and some other improvements.