More intuitive keyboard shortcuts for rotation

This patch manually assigns the accelerator for Rotate Left and Rotate Right.
The automatic acceleration sometimes assigns 'R' to Rotate Left due to it being first, which seems counter-intuitive to me.
This patch makes 'Rotate Right' as 'R' and 'Rotate Left' as 'L'.

Review request: http://svn.reviewboard.kde.org/r/5579/