Add a section summarising how options work, make the distinction between window and session options clearer, and fix the incorrect synopses and descriptions of show-options and show-window-options.
Add a section summarising how options work, make the distinction between window
and session options clearer, and fix the incorrect synopses and descriptions of
show-options and show-window-options.

klaxalk/tmux,klaxalk/tmux,klaxalk/tmux,klaxalk/tmux,klaxalk/tmux