emacs: Put the notmuch-go table in the minibuffer prompt

Previously, notmuch-go went through all sorts of shenanigans to put
the window with bindings help directly above the minibuffer.  This was
intended so I could make the bindings clickable and navigable like a
completions buffer, but that never came to pass.

Dramatically simplify the prompting code by putting the table directly
in the minibuffer prompt.
Put bindings in saved searches
Docs
Fix compile warnings
Add to build and default global key map
go -> jump
emacs: Expand default saved searches and add shortcut keys

This should help new users off to a better start with the addition of
more sensible saved searches and default shortcut keys.  Most existing
users have probably customized this variable and won't be affected.
Fix hello tests