Fix encoding issues when displaying time zone in Zenmap

[dmiller-nmap]

In this screenshot from an unrelated bug report, the time zone (Malay Standard Time) is not shown in the proper encoding in the Nmap Output window. We should be able to correct this by detecting and passing along the encoding in a few places:

• user's display encoding (Zenmap uses this properly as evidenced by the correct display of the translation language)
• terminal encoding info passed in the environment to Nmap (determines what encoding will be used to output the date)
• encoding used to decode the output of Nmap (this is probably where the fix should be).

The screenshot is on Windows, but Python environment should make it possible to do this in a portable manner.

[Varunram]

@dmiller-nmap When going through NmapParser, I noticed that we do pass sys.getpreferredencoding to zenmap. When I ran
time.strftime("%B %d, %Y - %H:%M").decode(locale.getpreferredencoding())
it seems to print the right output. And since it prints the first parts of the output correct, the encoding must have been passed on or else an error ("Unable to properly format host start time") would've been printed. Any suggestions as to where else the problem might be? And could this be remotely related to #638 ?

[heheda123123]

the same issue in windows cli version