GF Sets: Add required locl features, punctuation glyphs

@alexeiva I had a chat with @brawer today about `locl` features required for proper language support; I guess we should remove https://github.com/google/fonts/blob/master/tools/encodings/GF%20Glyph%20Sets/RECOMMENDED.md and make the corresponding `locl` features part of the requirements for the glyphs sets to be truly supported. Eg, https://github.com/google/roboto/issues/255

Edit: Sascha also proposed expanding the punctuation coverage to include everything in the Unicode General Punctuation Block ([pdf](http://unicode.org/charts/PDF/U2000.pdf)), all super/subscript digits (if not already specified in the GF sets) but probably not the 'supplimental punctuation block' ([pdf](http://unicode.org/charts/PDF/U2E00.pdf)) - see eg https://en.wikipedia.org/wiki/Full_stop :)

This is something I hope we can work on during this summer :)

cc @m4rc1e @graphicore @felipesanches @fonthausen @aoifemooney