[with patch; positive review] notebook -- new cell_resize doesn't respect %hide at the beginning of a cell

[was]

If a cell starts with %hide, it should not be shown unless it is in focus. The new cell_resize code doesn't respect this. To see this:

1. Load a fresh worksheet with %hide's -- none of them are hidden. Click on input cells then out hide them.

2. Resize a web browser window with %hides -- suddenly all %hide inputs are shown.

[was]

Attached patch does this:

trac #3053 -- new cell_resize doesn't respect %hide at the beginning of a cell

1. Fix the listed problem.
2. Fix the %hide styling a bit; make %hide be grey
3. Make %hide work consistently on new page refresh versus in a running worksheet
4. Make cell be resized when clicking on an input area. This makes editing a %hide much more natural.

[boothby]

nice!

[mabshoff]

Merged in Sage 3.0.2.alpha1