Simplified the view mapping (`w`) to not 'enter' the view window that is
opened by default.
What happened previously is that pressing the mapping
would open the view pane (or create a vertical/horizontal split and then
open the view pane within it if only one pane is visible) and then move
the cursor into it so that you can scroll within.
The issue was that to close the view pane again, one had to exit it
first (through `Shift+w`) which really hurt the quick-glance into a file
and then move on kind of workflow I mostly use previews for.
This commit simplifies the view mapping to allow exactly that, pressing
`w` still does all the things it did previously, only does not move
focus into the preview window so keeps the workflow simpler.
If given <nop> as prefix mapping, the suggestions box shows *all*
mappings that exist in the program. By removing the <nop> we make the
key do its usual action but at the same time restrict the suggestions
being displayed to those actually following the prefix.
