Add MiqWidget importing/exporting

Related to Bugzilla 1115106
https://bugzilla.redhat.com/show_bug.cgi?id=1115106

@gmcculloug @dclarizio @h-kataria Please Review.

Also note that the styling for the slick grid stuff is off, but I figured that could be fixed after this is in.
@Fryguy @jrafanie We're thinking of adding the towhat column to the scope of the validates_uniqueness_of :name for MiqSchedule. Do you foresee any problems or have any concerns with this?