When showing a message, if the user doesn't specify --decrypt= at all,
but a stashed session key is known to notmuch, notmuch should just go
ahead and try to decrypt the message with the session key (without
bothering the user for access to their asymmetric secret key).
The user can disable this at the command line with --decrypt=false if
they really don't want to look at the e-mail that they've asked
notmuch to show them.
and of course, "notmuch show --decrypt" still works for accessing the
user's secret keys if necessary.
Changed one tab in doc/man1/notmuch-show.rst to 8 spaces.
Removed one leading tab in doc/man5/notmuch-hooks.rst to make
the SYNOPSIS style consistent with other pages.
Previously, this was a verbatim copy of the --format=json text.
Change it to instead reference the JSON text and actually describe how
the S-expression format works.
This is the output from sphinx-quickstart, massaged a bit, along with
our existing man pages converted to rst.
A skeleton notmuch-emacs manual is also included. It is not suitable
for end user use yet.
