wr217292: use Strings rather than TimestampTZ types
wr217292: use Strings rather than TimestampTZ types

The problem with TimestampTZ is that it removes the ':' from time zone
offsets (e.g. +12:00 becomes +1200), at least when coercing from a
string to a TimestampTZ. This may not be desirable in some cases, and
we can deal with strings in most cases anyway, so it's unnecessary.

catalyst/XML-SRS