New command: AfterBars

I've added a new command: AfterBars.

The idea is that you can set "something" to happen at some point in the future.

For example, you might want to print a message to the terminal every 10 bars (nope, no idea why you'd want to do this). Or, more usefully, you may have set a song (or part) into a macro and want to change the volume of this after a few bars. So, you can now do something like:

   Mset  Melody
       C
       D
       .... more chord lines
   EndMset

And expand this melody a number of times:

    $Melody
    $Melody

and now, for the final loop, we change the volume after 4 more bars:

     AfterBars Count=4 Volume pp

And, now the command becomes cool.

You can even set a specific bar number (Bar=32) or repeat the command every nn bars.

I need to work on this a bit more and debug the line number settings before we get too excited. But, this will find itself into the next developer release. Hopefully, next week.

Standby :)