Added `local-time` option to cgitrc

When `local-time` is set, commit, tag and patch timestamps will be printed
in the servers timezone. Also, regardless of the value of `local-time`,
these timestamps will now always show the timezone.

Signed-off-by: Stefan Naewe <stefan.naewe@atlas-elektronik.com>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>