Resizable: modified resizable containment plugin to restrict resizing within container. Fixes #7018 Resizable: resizing can move objects

Just want to check if this approach is ok ?  for fiddle link - http://jsfiddle.net/dekajp/c2Rux/13/

adding `prevSize` and `prevPosition`  in the plugin parameter object. so that if resize breaks then it can be restored.

this PR is not complete - does not include unit testing. ( Fixes #7018 )