FS#3946 time zone for agent

added formatTimeTZ function to format hour and minutes
to the time based on timezone parameter
Added formatDateTZ to return date based on timezone parameter.
Added tzLocalDate to do the actual date conversion based on
timezone name and gmt time. Returns a date object
Added formatTimeTZ to return hour and minute string based on
gmt time and timezone.

Modified Calendar.feh to display date based on timezone if the
timezone is set.