Set position on document load only if no page was specified
Make inital values more explicit

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
CS

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
More consts

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Implement shortcuts for scrolling to page top/bottom