cli: add options --offset and --limit to notmuch search

cli: add options --offset and --limit to notmuch search

Add options --offset=[-]N and --limit=M to notmuch search to determine the
first result and maximum number of results to display.

Option --limit=M limits the maximum number of results to display to M.

Option --offset=[-]N skips the first N results; with the leading '-' skip
until the Nth result from the end.

Note that --offset with a negative N for thread or summary output requires
counting the number of matching threads in advance.

Signed-off-by: Jani Nikula <jani@nikula.org>