TimeZone support tracked in #148

[gautamsi]

discuss any issues with #148

[gautamsi]

TimeZone related code ported.
caveats:

1. You want to use ews.TimeZoneInfo.FindSystemTimeZoneById("zone id, Windows based or IANA id") It usage timezone mapping data generated locally from combination of unicode data and windows timezone information data
2. Local timezone can be created using TimeZoneInfo.Local and UTC timezone can be created using TimeZoneInfo.Utc
3. you can use static ConvertTime(dateTime: DateTime, sourceTimeZone: TimeZoneInfo, destinationTimeZone: TimeZoneInfo): DateTime to convert datetime from one timezone to another. please report any bugs.