Cleaning up moon.GridListImageItem to accommodate recent changes in enyo.GridListImageItem.

Also removing moon.GridList styling rules and renaming GridList.less => GridListImageItem.less, since we're removing moon.GridList in another open PR.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)
Merge pull request #1178 from enyojs/gridlistimageitem-graynorton

Cleaning up moon.GridListImageItem to accommodate recent changes in enyo...

Reviewed-By: Ben Combee (ben.combee@lge.com)