bookmark menu mode: be able to edit directly in bookmark-menu mode window

[Drew Adams]

For consideration after the release -

It might be convenient to be able to edit bookmark names and locations
directly in the bookmark-menu mode window, instead of using `r' and `R' to
change a bookmark name and location, respectively.

Have an "edit" command (e.g. bound to `e', instead of
`bookmark-bmenu-edit-annotation'). In the edit mode, characters would be
self-inserting within bookmark names and locations. `C-c' would end editing.

The advantage of `R' is that completion is available for navigating the file
system. The advantage of a simple edit mode is, well, simple editing (e.g.
of multiple names or locations).

WDOT?