Autosave: add failsafe check for files with identical names

Extremely low probability of this, but "better safe than sorry"
Integrate new Glass Tiles tool

@audioglider is starting to make me look bad with all these excellent
tools he's contributing.  Clearly I will have to step up my game to keep
pace with his great work... ;)

Glass Tiles is another excellent addition to PD's effects library.
Despite operating like a "distortion" filter, I have placed it in the
Effects -> Artistic category.  Other distorts with an artistic bent
(Figured glass, Kaleidoscope) also appear in this menu, in part because
I think it's a better fit, and in part because PD's Distort menu is
already abominably large.

One really great thing @audioglider has done on this tool is support
pixel supersampling.  I like his method so much that I will probably
steal it for a few other Distort tools, but in the meantime, I thought
it worthwhile to give this dialog a slider for quality, instead of the
usual "fast/quality" binary choice.  The new Quality slider controls the
number of extra samples taken for a given pixel.  Supersampling is
computationally expensive, but the end results are very nice, especially
for tools like this where destination pixels frequently represent
10-100x source pixels.

Anyway, I hope the sliding quality scale provides a good compromise for
users with slow PCs and users with fast ones.  Thanks again to
@audioglider for another brilliant addition to PD.