Improve saving UI

[Stuart Langridge]

The saving UI pops up a textarea for cut-and-paste; improve this (so that text in the textarea is selected by default; perhaps text is in a very small font so that it can all be seen).

If it's possible to actually implement "save this page" from JavaScript, do it, but I don't believe it is. (IE can do it with execCommand("SaveAs"), but WebKit can't.)

[Stuart Langridge (sil)]

Perhaps build a web service (on, say, App Engine) which can take a POSTed block of HTML and then serve it back with Content-disposition: attachment. Then, if we're online when saving, use the web service; if not, pop up the textarea.