Please test: fix for cut node resurrection & new refresh-from-disk command

[Edward K. Ream]

Here is the checkin log for rev ea203f8... All tests pass.  Please report any problems immediately.

QQQ
Fixed bug 1090950: refresh from disk - cut node resurrection.
https://bugs.launchpad.net/leo-editor/+bug/1090950

refresh_rclick_cb in contextmenu.py now just calls c.refreshFromDisk,
which calls c.recreateGnxDict() before reading any file.

Also created the new refresh-from-disk command and the corresponding item in the File menu.
QQQ

When the dust settled, this was a straightforward bug to fix.  However, I did spent several hours in background work.  This work included the new code enabled by the g.new_gnxs switch.  I'll leave the switch in for at least several days.  Eventually the old code will be removed.

Also, I added a tempOutline keyword arg to c.pasteOutline and fc.getLeoOutlineFromClipboard, telling these not to update fc.gnxDict when pasting a temp outline.  This isn't strictly necessary for this particular bug fix, but it might prevent strangeness in other situations.

Edward