bitbake: toaster: Make "Edit columns" multiselect

bitbake: toaster: Make "Edit columns" multiselect

Twitter Boostrap elements with the dropdown-menu class
close by default once a selection is performed. Such
behaviour is not appropriate for our "Edit columns" menu,
since users might want to check / uncheck several
columns.

This patch adds a call to the stopPropagation() jQuery
function to main.js to stop the "Edit columns" menu
from closing every time you change a checkbox.

(Bitbake rev: c2e43750bf0913523a1abcb2c8bf97b764da2524)

Signed-off-by: Belen Barros <belen.barros.pena@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>