Store kernelspecs under jupyter, not IPython
Add kernel directory relative to sys.prefix
Default to systemwide installation for kernelspecs
Update kernelspec command line interface
Update kernelspec tests
add ability to unregister a preset

fix #7218
Revert change to test skip condition

This was part of a commit cherry picked from another branch, and this
change didn't make sense on this branch.
make global css change on command/edit mode
correct variable name
binary or is rare in JS
Actually test that the j-nth cell.
Merge pull request #7274 from Carreau/global-command

make global css change on command/edit mode
Merge pull request #7203 from takluyver/kernelspecs-sys-prefix

Look for kernelspecs relative to sys.prefix
Merge pull request #7287 from Carreau/mistake

binary or is rare in JS
Merge pull request #7251 from Carreau/unregister-preset

add ability to unregister a preset
Fix crossreference to %run magic
MAINT: Move `update` from FileContentsManager to ContentsManager.

The implementation in FileContentsManager is written entirely in terms
of the required API, and is sensible for other ContentsManager
implementations.
Merge pull request #7308 from Carreau/reform-css

reformat css
Merge pull request #7312 from quantopian/refactor-contents-update

MAINT: Move `update` from FileContentsManager to ContentsManager.
unify submenu style with menu style

closes #7303.

Also change the arrow that indicate submenu for a fontawesoem icon,
instead of the ugly hack that show only the left border of a rectangle element
which with is twice the one of its border to get a triangle.