Don't use source file name to build binary file name

Currently the font file gets its name from the source file, which can lead to a conflict when the designer has a very strong opinion about how the source files should be named. Also since we onboard only binaries for now, we shouldn't be that strict with the source file names (or we can make exception if the designer feels very strongly about it).

So if we have for example `FamilyNameSomething.ufo` or `FamilyName-Something-Italic.glyphs`, ideally, the font file name should follow the pattern `FamilyName-StyleName[axis].ttf` regardless of the source file name. Presently, it would end up with `FamilyNameSomething-StyleName[axis].ttf`.