New Utility tracks

I've added 3 utility tracks to my DropBox account (of course, permission granted to copy these to the community site).  Full pics, readmes, and the tracks at: https://www.dropbox.com/sh/yd5a5v37c6bz2sd/AAD9m1W7lSUnSixx5ZjfZeWFa?dl=0

• 101_dirty.thr - Just leaves the ball at rho=1, no patterns, no cleaning.  Useful when you have a pattern that creates it's own background, but wants to start at 1.
• 010_dirty.thr - Just leaves the ball at rho=0, no patterns, no cleaning.  Useful when you have a pattern that creates it's own background, but wants to start at 0
• inwards_subburst.thr -this could also be called "that track which pushes sand back into the center".

  A lot of tracks tend to push the sand from the center of the table outwards (especially my "Sunburst" track). Getting the sand evenly distributed means taking the glass top off and smooth it. PITA.

  I realized that inverting my "Sunburst" track would push the sand back into the center, so I added a flag to invert it, and viola - "Inwards Sunburst".

  By the time this is done, you'll have a little mountain in the center of your table. The ball might not be able to go through this the first time, but a run of the "clean" track or several others will clean this up in a cycle or two.

  Enjoy!