Added missing release dates to Changes file (from BackPAN)

Various changes, but the main one was adding a load of missing dates from BackPAN (from you and YOSHIMI). I'd been putting off updating my script to go get BackPAN details for potentially multiple authors, but decided to bite the bullet tonight.

I enjoyed some of your venting in the Changes comments :-)

I marked 0.49 as 'not released', since it wasn't on BackPAN. In those situations some authors prefer to merge the changes into the next release that made it to CPAN. Do you have a preference?

Neil