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.
@eclarizio Yes, this lookup still needs to specify the :towhat condition otherwise if a similar named MiqReport schedule exists it will get picked up.  It look like the userid column is not being used for the widget miq_scheduler instance since creating one in the UI sets it to 'system' which is coming from the default_value_for setting.