created text serializer variant which includes creator

the default text serializer does not include creator information (for
historical-evolutionary reasons, mostly[1]) - which we want to be
included for tiddler files created by this store though

[1] Is this too late to change now, @cdent - seems that would make the
serializer more generic/accurate? (Of course such a change would require
adjustments to the default text store.)
ensured origin information is retained properly

storing the creator (just like created) in each revision rather than
calculating it from the first revision - that not only makes each
revision independent of others, there's also no overhead due to
revisions being stored as deltas

note that, unfortunately, the test introduces a 1 second delay here -
this annoys me greatly, but there's nothing we can do about that short
of increasing timestamp resolution