Add cylinder layouts & a script for generating them

Added some layouts:
```
circle_r1_50x.l
cylinder_r1_h1_64x20.l    // rad 1, height 1, 64 pix around, 20 pix tall
cylinder_r1_h2_32x20.l
cylinder_r2_h0.5_128x10.l
```

And the script that made them:
```
Usage: make_cylinder.py [options]

Creates a cylinder on the z axis extending from -height/2 to height/2.
n_tall is optional -- it will default to a value that creates square pixels.
You can also create circles by setting height to 0.

Options:
  -h, --help           show this help message and exit
  --radius=RADIUS      radius of cylinder. default = 1
  --height=HEIGHT      height of cylinder.  default = 1
  --n_around=N_AROUND  number of pixels around the circumference.  default = 32
  --n_tall=N_TALL      number of pixels from top to bottom. (optional)```