VIM-407 Add tests. Only skip the ending line if it is empty.

This change only skips the last line of an indent range if the line is empty. Previously the line was skipped if it was one character long (thus VIM-407). I added selection tests for the right shift action to help me understand why the final line was *ever* being skipped. It appears that the original author's intent was to avoid indenting a final line that was empty.

This is my first ideavim patch, and I don't know the editor API very well, so I'm interested in what you think of the approach.