Ive previously submitted a patch to improve the formatting of multiline properties in the emailed change note.... this patch improves the presentation of these properties in the history display.

This patch uses difflib to break the change into added and removed lines. removals are displayed in strikethrough, and additions are given a yellow highlight.

One aspect of this patch could use additional review..... The 'current' dictionary always originally stored the property values *after* being passed through cgi.escape, however this feature needs to calculate the diffs on unescaped strings, therefore the hyperdb.String case now stores unescaped strings in that dictionary. It is obviously critical that input strings do not leak into the ouput html stream without passing through cgi.escape.