[Epiphany] (no subject)

[<bordoley msu edu>]

Adds a help => contents menu entry and I implemented call back stubs,
but didn't bother actually implementing it since we don't have help docs
yet anyway.

Changes the tab switching modifier to alt as specified in bugs 105938
and 87764. This change is needed because in a scrolled window,
ctrl+pgup/dwn should vertically scroll, though there is a mozilla bug
that keeps this from working.

dave