Improved wording for Guide chapter 5

[Andras Farkas <deepbluemistake%gmail.com@localhost>]

On
https://www.netbsd.org/docs/guide/en/chap-boot.html#chap-boot-editing
line orientated -> line-oriented
a very simplistic text editor -> a very simple text editor
screen orientated -> screen-oriented

Further down:
https://www.netbsd.org/docs/guide/en/chap-boot.html#chap-boot-keyboard-layout
italian -> Italian

Further down:
https://www.netbsd.org/docs/guide/en/chap-boot.html#chap-boot-system-time
The one reference to "GMT" *might* perhaps be better as "UTC".

Further down:
https://www.netbsd.org/docs/guide/en/chap-boot.html#chap-boot-pkgsrc
The examples for pkgin search and pkgin install use different examples
in the text and the code. (stat vs WORD, fscd vs fluxbox)  That should
probably be fixed.

Further down:
https://www.netbsd.org/docs/guide/en/chap-boot.html#chap-boot-security
The link to
http://www.netbsd.org/support/security/
should probably be changed to
https://www.netbsd.org/support/security/
though that's an optional sort of change.

Further down:
https://www.netbsd.org/docs/guide/en/chap-boot.html#chap-boot-rebooting
I think that a 'shutdown -p now' and 'poweroff' example should be
added to the other two.

Style-wise, I think it may be better to use "man page" than "manpage",
which occurs three times in this chapter.