Code review comment for lp:~mardy/unity-2d/rtl

* arrow_rtl.png is not an exact mirror of arrow.png because arrow.png has had an update recently
* panel/CMakeLists.txt lacks a directive to install panel/artwork (see launcher/CMakeLists.txt for reference; thinking about it divider_rtl.png is probably useless now :)
* Individual changes to places.cpp, launcher.cpp, etc. should be factored in Unity2dApplication:
    Unity2dTr::init("unity-2d", INSTALL_PREFIX "/share/locale");
    if (u2dTr("QT_LAYOUT_DIRECTION") == "RTL") {
        QApplication::setLayoutDirection(Qt::RightToLeft);
    }