added global composer prestissimo for parrallel composer processing

[james-nesbitt]

This adds prestissimo to solve composer performance issues, as detailed in https://github.com/wunderkraut/wundertools-image-fuzzy-developershell/issues/38

Thanks to @badrange for this suggestion.

[aleksijohansson]

Tested and benchmarked. Seems to reduce the wundertools init command execution time on OS X by 30%.