New and improved assetManager

I've tweaked the assetManager tool to improve the functionality of
mail-to-blog posts. You can now specify a post title in your email
message by simply appending the title after the secret subject. So
simple, why didn't I think of it before! The assetManager matches the
secret subject against those you set for your weblog categories then
strips it from the email subject line. Whatever remains becomes the
title of your post. Also, any attached pictures are now stored in a
dated folder hierarchy rather than all in the same directory. This is
something I should have done ages ago but have only just got around to
it.