SLING-3666 : supporting changing of the multiple mode in the jcr properties view - plus resized those columns to have header properly visible - note that for new rows the flag is not yet changeable until the value is added to the underlying .content.xml (atm)

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1602333 13f79535-47bb-0310-9956-ffa450edef68