quick launch project when user right-clicks on an existing uproject file

[ScottKirvan]

To round out the feature set, and because I know my muscle memory will make me do this, also launch the project when you right click directly on a uproject file.

This is a change to the installer (adding the registry hook for the right-click-on-file), and to the quicklaunch batch file (code below)

Note
I had implemented this, but it conflicted with Unreal's own registry entries, so do lots of testing if you add this one.

if %mode%==ON_UPROJECT (
    echo.Launching: "%projectName%"
start "" "%projectName%"
REM )