Set timezone in case of express installation

This currently only works for Fedora.

* Anaconds seems to expect full name of the timezone rather than
  abbreviation but it seems to accept and use abbreviations too.
* Doing this for windows is another story: Windows XP/2k/2k3 would want
  some custom integer ID(1) and Windows 7/2k8 would want some long
  string name(2).

1. http://blog.williambritt.com/index.php?/archives/23-XP-Unattend-Timezone-Settings.html
2. http://technet.microsoft.com/en-us/library/cc749073%28WS.10%29.aspx

https://bugzilla.gnome.org/show_bug.cgi?id=665803