Undocumented `autohintOTF` fails many builds

[bramstein]

A lot of our builds are failing with the new gftools version because it tries to run psautohint on the OTF files and many of our source files are not set up for this.

For now we can disable this behaviour by setting autohintOTF to false, but it would be good to review why this is now default and perhaps document it.

[simoncozens]

You're right, this should be disabled by default.

It was default because I thought (a) auto hinting OTFs was probably a good idea (and someone asked for it), and crucially (b) because I thought psautohint was similar to ttfautohint in that you can just run it and it hints stuff automatically. I didn't realise it needed set up. I'll turn it off.