MUMUP-1362 : Implement ui-sortable for drag-drop

## Dev Notes
+ Using https://github.com/angular-ui/ui-sortable
+ Drag starts on pressdown-hold
+ Just clicking will do the expected behavior (expand for simple content portlet, max mode portlet, or flyout for external)

## Screenshots

### LG Screen
![drag-drop](https://cloud.githubusercontent.com/assets/3534544/5190562/6ac21408-74ac-11e4-9bc6-8839498b4563.gif)

### MD Screen
![md-screen-dd](https://cloud.githubusercontent.com/assets/3534544/5190630/10325498-74ad-11e4-9e13-a510e987f0b2.gif)

### SM Screen
![sm-screen-dd](https://cloud.githubusercontent.com/assets/3534544/5190643/2ed8c9a4-74ad-11e4-81ed-938bc4967dca.gif)