Add voltLib.voltToFea module and command line tool

[khaledhosny]

A tool for converting VOLT VTP projects to feature files.

Essentially https://github.com/TiroTypeworks/TiroTools/tree/master/Volto with minor modifications to fit into FontTools.

[behdad]

Maybe a more descriptive name?

[khaledhosny]

I have no particular attachment to the name, but it is the name used over at https://github.com/TiroTypeworks/TiroTools

[anthrotype]

how about moving it inside voltLib and renaming the module voltToFea, like the class is also called?

[khaledhosny]

At one point it was supposed to grow a fea to volt convertor as well, and may be even a volt compiler. This didn’t happen though, and no idea if it ever will.

[anthrotype]

We could add more submodules if/when needed. I think having a both a fontTools.voltLib and fontTools.volto is confusing and one "volt" too much for the top level modules.

[khaledhosny]

We could add more submodules if/when needed. I think having a both a fontTools.voltLib and fontTools.volto is confusing and one "volt" too much for the top level modules.

Done.

[anthrotype]

LGTM! Many thanks to Khaled and TiroTypeworks for contributing this to fonttools!