Fixes bug #990: SC.ListItemView Doesn’t Render Right Icons of the View’s rightIcon Property

The code for rendering a right icon was missing in the render method.
It has been added. Additionally the first part has been adapted to the
code for the (left) icon: In case of contentRightIconKey, it is only
rendered if a value exits for that key.
Minory cosmetic change

Added a space.
Bug #990: Adds unit test

Adds all unit tests for rightIcon of SC.ListItemView.