more emacs-like find/find next

[Rob McMullen]

I had an idea how to implement some improved key processing, so now
the same keystroke that pops up the minibuffer to find a text string
will also find the next match if the find minibuffer is already
active. Also, I added a new action to search backwards.

Still plan on adding shell style regex and full regex matching.

Oh, also, M-ESC ESC now cancels the minibuffer (or any other action)
no matter where you are. Previously the focus had to be back on the
main window -- if the focus was in the minibuffer, it wouldn't work.

I haven't gotten around to fixing the replace minibuffer yet (it's
still using the old PyPE replace bar), but that's next. I'm going for
a very emacs feel to it: everything controlled by the keyboard.

Everything is in the latest svn.

Rob