Typo fix and try to be more explicit.

Try to be explicit at redirection doc.

Provide new keyword stdin, stdout and stderr at -o options.
Decrease number of logger line to display to 10.

Allow to use an existing snapshot at upgrade time

create, restore, remove and list are available.
These subcommand do not affect the state of a running services.

Typo fix

In addition to the string "@I" as identifier to replace by the name of instance service,
the following identifier are now recognize :
@I, @U, @u, @G, @g, @H, @S, @R. see doc/66-identifier.md for furthers information.

Rename TimeoutKill to TimeoutStart.
Rename TimeoutFinish to TimeoutStop.
Remove TimeoutUp and TimeoutDown key.
To avoid confusion and mistake, oneshot and classic service use now
the same key name to declare the timeout to use.
TimeoutStart and TimeoutStop are clearer than TimeoutKill and TimeoutFinish.
66 is sufficiently smart to name the file correctly for s6-supervise
whick look for the timeout-kill and timeout-finish file.

The status command without options return now an overview of all services
from all trees. This is similar as 66 tree status command but with a
shorter call and less informations.

Provide more explanation of environment behavior and new scandir behavior

This reverts commit 87bd69c6.